Frequently Asked Questions (FAQ)

Why can't I get it to automatically install from the USB?
The issue for USB buyers is that I can’t depend on an autorun file like on a CD since Windows does not look for one.  Therefore, the user has to find and run the installer file: 00_SeaMarksSetup8.exe. Since Windows often sorts the files alphabetically, that file should be located at the beginning of the list.  The install compiler includes two more like named files one of which is identified as a Windows installer.  That is not the one to run.  The one called an application is the one to run.  Secondly, it is best to right mouse click on this file and select “Run as Administrator”.  That insures that all files get properly installed and registered with windows.  .
Does it work with Windows Vista/7/8/10?
Yes. It was created in Windows 7 and it works good. My customers have tried it on the Windows 8  and 10 with no problems.  I recommend upgrading from Vista on an older computer. Vista can cause some bizarre behavior.  If you have Windows XP or 7, I recommend you stick with it until you get a new computer.
Will it work on a MAC or a Linux?
It will run on Intel based MACs using CodeWeavers’ CrossOver for the MAC. See this article on installing on a MAC. If you want to go this route, go to: Codeweavers to get it.

They say: “CrossOver allows you to install many popular Windows applications on your Mac or Linux computer. You can think of it as an emulator, but it’s different, because there’s no Windows OS license required. Your applications integrate seamlessly in OS X or Linux; just click and run. No rebooting, and no switching to a virtual machine

CrossOver costs about $60 and does not need a copy of Windows to work. MAC owners could alternatively use a Windows emulator like Parallels, Fusion, or dual booting to run it but these require you to purchase a legal copy of Windows. A cheaper alternative is to purchase a used laptop with Windows XP.

Can I run it on more than 1 computer?
Yes. Many of my customers want to run it on a home computer, a work computer, and possibly a boat computer. That is permissable. Each program is shipped with either your name.address or a serial number on it. That way, the registration can be confirmed as to the legal owner.
Will Loran come back?
It is turned off in the USA as of Jan 17, 2011.  They have destroyed some of the stations, so it is questionable that it will be resurrected in the US.  It will remain on in S. Korea, and Europe.  However,
House Committee Moves to Block Loran-C Teardowns  2/14/2014 To preserve for possible use in GPS backup system.  See: http://www.insidegnss.com/node/3913 Under Congressional Pressure, U.S. Agencies Maneuver on eLoran Relaunch, GPS Backup 10/30/2014 Prodded by Congress, the federal government is reexamining its decision to abandon eLoran, a network of ground stations capable of supplying essential timing and positioning data to power, phone, and other critical networks if something happened to GPS.  See:<http://www.insidegnss.com/node/4263>

DoD Seeks Sources for 50,000 eLoran Receivers  1/14/2015

In a nod to the usefulness of international enhanced Loran (eLoran) systems the U.S. Department of Defense (DoD) in January began a search for companies able to supply some 50,000 eLoran receivers. Meanwhile a multi-agency team continues sketching out the structure of a potential U.S. eLoran system for federal officials weighing a relaunch of the program as a backup to GPS.

see: http://www.insidegnss.com/node/4372

Will Loran remain in other countries?
Short answer, yes, as eLoran

UK eLoran Now in Operation to Back Up GPS

Technology to counter the threat of GNSS jamming is now available at Dover and along the east coast of the United Kingdom as the island nation continues to implement an enhanced Loran (eLoran) system that is setting an example for the world. See:<http://www.insidegnss.com/node/4264>

June 2013 North Korea’s GPS Jamming Prompts South Korea to Endorse Nationwide eLoran System

Why did my loran 9960 or 8970 points move?

It was not your Loran!

If you used Loran Chains 9960 or 8970 and noticed that your waypoints were all off by 600 ft or so after 1/17/07, blame the Department of Homeland Security not your Loran. On January 17, 2007, the DHS changed the way the loran stations work for these chains and as a result, your observed 9960 waypoints were off by about 0.5 us on the Xray line and 0.3 us on the Yankee line. See the article:time_of-transmission.htm . I have a fix for this situation starting in version 7.0. The DHS subtracted 0.5 us from the 9960Xray number and 0.3 us from the 9960Yankee number Therefore, your waypoints taken after 1/17/07 will be off by about this amount.

The program now has two entries for 9960 and 8970. For example, there is 9960b for the before case and 9960a for the after case. By making your User Preferences include both, you can handle either case. You can also calibrate for either or both.

Winter/Summer values

EC NEWELL MAN » Fri Jan 22, 2010 on  fishingunited.com/forum/  wrote:”I should point out a variation in Loran C numbers which we knew about for years.  Many wreck fishermen from Shinnecock out east to Southern Massachusetts were familiar with getting both a SUMMER and a WINTER set of Loran C numbers for their favorite wrecks and rock piles. As many of these wreck fishermen learned, their Loran TDs would vary over the year from a few tenths off since a shift would occur as the numbers would shift south and east in the winter (down in tenths), then revert back north and west to the summer numbers (up in tenths). One wreck in particular, the Cable Wreck, was notorious for ‘disappearing’ when fishermen were given the numbers to that spot and not told when that set of numbers were taken!”

I sent this author an email that said:  “I was browsing the web when I came across an interesting comment on your Jan 22, 2010 electronics forum. You mentioned that Loran C numbers have a summer and winter set in the Northeast. I hadn’t heard this before and it was not my experience in Florida. However, it makes sense if you consider the varying effect on the loran signals by the change in foliage. That doesn’t happen here, but does where you are.”He further said in a communication with me:

“A prime example is the Cable Wreck which is east of Block Island RI, south of Cox Ledge.

Now I know you are as sharp as they come with this, so we see the offset easily and the shift from summer to winter for a wreck that went down in 1958, and is only 61 feet long….she has been reduced to bare bumps on the bottom, most likely her keel and steel (engine block/frame/fuel tank etc.  giving any indication of her finally resting place:

Winter # 14493.2  43736.0

Summer # 14493.3-4  43736.4-3

Notice you have to figure in a greater offset on the 43 line.

This offset holds true from roughly Shinnecock through Cape Cod, and I can tell you that a famous wreck off Nantucket in 40 fathoms, the Republic, as big as it is, has also a summer OFFSET from the conventional TD numbers!

Another reason why when looking for wrecks, or doing conversions as your program does, there is a difference in accuracy with the 14 000 line and 25 000 line as it carries off to the east…as you go east of Shinnecock, the accuracy of each tenth lessens in distance from roughly 50 feet, to 60, 70 and at times greater than 70 feet between tenths on that 25 000 line. It is the reason why when wreck hunting from this region, that you shy away from the 25 000 numbers which some draggers would use, and concentrate on the 14 000 number because of the inherent higher accuracy per tenth.

Just think about it, and you touched on it….in this region we have the big hills of the New Jersey Highlands which screws up any TD’s you convert in and around the Sandy Hook region….we have offsets shift here  when moving to another spot a few hundred feet away, but thankfully land ranges (radar distance) can sort this out if you take them!

I can tell you many stories about shifting wrecks, and one last one is about the Great Lakes Barges in Ambrose Channel here in NY……this darn thing moves a few tenths (its one of the most noted for shifting until GPS came along)…it’s two wrecks which lay NW to SE, separated by a short distance…yet you would miss both of them if you didn’t remember the way numbers SHIFT during the season.”

How accurate is the Conversion from Loran to GPS?
The SeaMarks program automatically converts Loran to Lat/Lon or Lat/Lon to Loran and saves both in the waypoints (aka readings) file. If you enter both Loran and GPS for a given spot, it is considered a calibration waypoint and no conversions are performed on it. The conversion equations the program uses were developed by the Navy years ago and are quite complex, but they are the most accurate available.  For more information on the Loran C system, consult the Loran-C users handbook.
The conversion accuracy approaches the basic accuracy of Loran if you are using calibrated Additional Secondary Factors (ASFs). The program comes with a set of ASF tables developed by the Defense Mapping Agency in the 1980s that are good to about 250 ft of accuracy.  The program has also been pre-calibrated for certain areas where data was made available to us, improving the accuracy in those ares to close to that of Loran.    ASFs are correction factors and are used to compensate for the fact that the theoretical Loran number (based on the speed of light over salt water) is a little different from the Loran TD number you get on your Loran set. Land masses of various wetness, mountains, power lines, and cities will delay the Loran signals as they travel to you. This delay can change the observed Loran number by as much as 5 microseconds and will cause the Loran to Lat/Lon conversions to be less accurate than they could otherwise be. The delay is, however, usually very stable and repeatable. So, old loran numbers are still good.  For a graphic example of what the correction factors are and how they change over an area, check out the ASF charts for the Gulf of Lawrence as provided by the Canadian Coast Guard. Area3ASF_5930X.pdf, Area3ASF_5930Y.pdf, and Area3ASF_5930Z.pdf.  These charts illustrate that the corrections can get large in some areas and depend on which loran slaves you are using. Look at all three charts to see how the ASFs change and how much they change over the area. Remember the ASFs are in microseconds, and one tenth of a microsecond of error is (approximately) 40 to 120 ft depending on the geometry of the lines. A description of how the charts were created was presented in 1988 by David Gray at the Wild Goose Association annual meeting: “ASF Chartlets, a Picture is Worth 1000 Numbers“. For the ASF tables covering the US, you can download our ASF display utility that is also a part of the SeaMarks program.

Note that the conversions cannot get any more accurate than the original Loran waypoints were. That is if the Loran waypoint got you to within 70 feet, don’t expect a converted waypoint to be any better than that even if you use a WAAS GPS receiver to find it. The SeaMarks program comes pre-calibrated for several popular areas. More areas are being added as data becomes available from users who donate calibration waypoints. If you are operating in one of the areas where pre-calibrated ASF tables apply, then you will get better conversion accuracy than with the uncalibrated tables. Calibration extends out about 40 miles from where the calibration data is available.

176_Calibration-SE-US 157_Calibration-NJ-NY 176_Calibration-NC-SC

Many Loran and GPS sets have either a built in table of ASFs or provision for entering them. NOAA charts that show loran lines were usually corrected for ASFs but they did not give any clue as to the correction used. NOAA once published ASF tables that were the basis of the built-in tables we use. With the help of Point Systems Inc. we scanned them in and OCR’d them to make the tables the program uses. These tables cover many of the commonly used Loran chains, specifically: 5930, 5990, 7960, 7980, 8970, 9940, and 9960. These tables are reasonably accurate, but your own data can be better. The government tables were generated in the 1970s using Milligan’s method. This consists of measuring, on a chart, how many miles of wet land, dry land, ocean, and cities the signal travels over for each point and then calculating the delay with Milligan’s formula. For you, the most accurate method for determining the ASF factors is to calculate them based on local reference points for which you know the both the accurate LAT/LON (preferably taken from a Differential or WAAS GPS) and the Loran numbers taken with a real Loran set. Enter both the GPS and Loran numbers as you enter your waypoints. Do this for many spots over a broad area to get the best results. Once you have entered the data, run the calibration routine.

Land based reference points are not desirable since the ASFs change rapidly near shore. Indeed, the government ASF tables do not cover land areas. A DGPS or WAAS waypoint is the best source of Lat/Lon, whereas a standard GPS waypoint is little better than Loran in accuracy. DGPS and WAAS can provide 15 ft. accuracy where it is available. Whether or not you use non differential GPS, take several waypoints so that the program can average the ASFs calculated from them and the Loran numbers and get better results.

When using the SeaMarks program to convert Loran chain numbers, it is possible to achieve an accuracy of better than 0.2 microseconds for “C” waypoints (about 100 ft.) and 2 microseconds for old “A” numbers. Keep in mind that the old “A” numbers were never very accurate to begin with and the calculations do not improve on that accuracy even if they are carried out to lots of decimal places. The same caution applies to Loran C waypoints.

Care should also be exercised when comparing our LAT/LON conversions with those of your Loran or GPS or other sources such as published lists and maps. Only if they are using the same ASFs and the same formulas will they be in close agreement. Only if the source specifically says that these were measured with both a GPS and a Loran can they be trusted. Since different Loran or GPS sets may use different ASFs and different methods of calculating, they will not necessarily agree with this program, other Loran sets or a GPS. Some older Lorans and plotters used simplified conversion formulas that have a significant error when used near the loran stations. For this reason, most fishermen preferred to record waypoints by their Loran numbers rather then by computed LAT/LON. GPS waypoints are in LAT/LON and are very accurate providing that you use Differential GPS (DGPS) or Wide Area Augmentation System (WAAS).

To recap, the reason ASFs are needed is that the Loran waypoints you get at any point differ from the theoretical predictions by an amount that depends on how far over land and over water the signal travels getting to you. Basically, this means that the signals do not travel at the speed of light in a straight line, as radio waves should, but travel somewhat slower and curve around the Earth. As they travel over the Earth’s surface (which is slightly conductive), they are slowed down. The equations used in this program are corrected for an all sea water path. The built-in Additional Secondary Factor (ASF)  tables provide the corrections for propagation over dry and moist land, lakes and cities.

For further information on Loran C and the conversion issues for US and Canadian waters, see: Canadian Coast Guard Radio Navigation  This site offers information on radio aids to marine navigation and part 6 is on Loran C and has the charts of coverage and ASFs. Readers are cautioned that the accuracy tables therein show what you would get if you did not use ASF corrections. Another reference for Europe is: New ways of looking at Loran-C ASFs .

We cannot recommend calibrating your conversions based on data taken from dubious sources or over land, so be sure that calibration waypoints are from real measurements at sea.  You do not need to calibrate if the accuracy you get in your area is OK

What Loran chain should I use?
For the USA, the Loran system covers most of North America as shown below. Loran chains are represented by the Group Repetition Interval (GRI). This represents the period between radio pulse groups sent by the master and slave stations in the chain. For example, the Southeast is covered by the 7980 chain. This chain radiates pulses every 79,800 microseconds. You normally will not need to specify the chain as the program will attempt to interpret the data in the most likely chain.


A chain consists of a master station and from 2 to 5 slave stations. The stations are located hundreds of miles apart and provide coverage up to 1000 miles. For example, the 7980 chain is served by a master in Malone FL, and 4 slaves in Grangeville LA, Raymondville TX, Jupiter FL, and Carolina Beach NC. They are known as the Wiskey, Xray, Yankee, and Zulu slaves. You need to use two slaves to get a fix. So, on the East coast between Jupiter and Carolina Beach, you would use the 7980Y and 7980Z slaves.


Anomalies do exist in certain areas regarding the selection of a pair of stations. Local knowledge may suggest that a pair, other than those indicated below, are the stronger pair.


The 9960 chain gives the best coverage in Lake Ontario and in Lake Erie. 9960W and 9960Z is the preferred pair in Lake Ontario. 9960Y and 9960Z is the preferred pair in Lake Erie.

8970X and 8970Y is the only reliable pair for Lake Superior and Lake Michigan.

Lake Huron falls in the coverage area of both the Great Lakes Chain (8970) and the Northeast Chain (9960). 8970X and 8970Y is the preferred pair but the 9960W and 9960Y pair also provides strong coverage in the southern part of the lake.


The preferred coastal LORAN-C pair from the Canadian Border to Nantucket Island is 9960W and 9960X, close to shore. 9960W and 9960Y give reliable coverage further off-shore.


From Nantucket to Cape Hatteras, NC, the preferred pair is 9960X and 9960Y.


From Cape Hatteras to Fort Lauderdale, Fla. the preferred pair is 7980Y and 7980Z.

There is some overlapping coverage between the Northeast chain (9960) and the Southeast Chain (7980). South of Cape Fear, N.C. to Brunswick, Georgia, 9960X and 9960Y can be used offshore. Closer inshore from Cape Fear to St. Catherine’s Island, GA., 9960Y and 9960Z is the preferred pair.


From Fort Lauderdale around to Cape Sable the preferred pair is 7980W and 7980Z. 7980W and 7980Y provide the most reliable coverage along the entire west coast of Florida from Cape Sable to Panama City.

From Panama City to Mobile, Alabama, the preferred pair is 7980X and 7980Y.

In the western Gulf of Mexico from Mobile to Grangeville, Louisiana, the preferred pairs are 7980W and 7980X. From Grangeville to Brownsville Texas, the preferred pair is 9610Y and 9610Z.


5990Y and 5990Z is the preferred pair from the Canadian Border along the Washington State Coast down to about 44 degrees latitude (along the Northern Coast of Oregon). 5990X and 5990Z give a strong fix further off the Washington and Oregon Coast.

Off the southern portion of the Oregon Coast and the extreme northern portion of the California coastline, 9940W and 9940X provide the best intersections.

9940W and 9940Y are the preferred pair along the northern California Coast to just below San Francisco. 9940X and 9940Y is the best pair off the coast of southern California.


If you have really old data, it is possible that the waypoints are from a now obsolete chain. For example, from 1966 to 1978, the East and South East US was covered by the 9930 chain. Data on this chain is available in the program and it can be converted to Lat/Lon. Some other obsolete loran C chains are lost in antiquity and insufficient data is available for them. During that time, the Loran system was in transition and they were experimenting with the setup or were stretching the capability to cover more area with the fewer transmitting stations they had.

For Loran A coverage, consult the following graphic:

loran-A-coverage area

Loran A used two station pairs to get a fix. For example, for Tampa on the West coast of Florida, the typical pick was 3H0 and 3H1.

The SeaMarks program will help you find the right chain and slaves for your area..

What if some waypoints fall outside the ASF tables?
If you have waypoints falling in areas where no ASF tables exist, then you will see an increased error in the conversions. You will also see a note at the top of the screen indication that no ASF table was found (for some of your waypoints). If the ASFs for that area are, for example, 2.0 microseconds and the Loran line spacing is 10 microseconds per mile, then you will have an error of 1/5 mile if 0 is used for the ASFs. In this case, you can use the single ASF per file method of applying ASFs and that will eliminate most of the error. Here, you set the ASFs for the whole file area. You can use the nearest good ASF from the tables or you can derive the ASFs by calibrating on some known reference points in the area. It is good practice to keep these waypoints in a separate file from those that fall in areas where the calibrated ASF tables exist. The ASF examiner will show you what tables do exist (or you can check the graphic link below), so you can make that determination. Also, the program shows a warning when, during conversions, it encounters waypoints in a file falling outside the area covered by the tables. One other aspect of this problem is that if waypoints fall very close to the boundary between an area having ASF tables and one that does not, then the conversions may fail. If you get a file where some points just do not convert, then sort the file by latitude and split out those points that did not convert along with any that fell outside the tables completely. Then change the conversion method for the file with the bad points to use “one ASF per file” and recalculate the Lat/Lon. This file of points can then be recombined with the rest as long as you do not do a “recalculate LL” or calibration on the file afterwards.

Click here to Examine ASF table coverages these figures show the original pages of the ASF tables issued by the government....

Does it work in Europe or Asia?

Yes, it is targeted world wide.  We have many non-USA customers, but do not have NOAA or 2D bathymetric charts for anywhere but the USA.  It does have simple charts that consist of a coastline, Lat/Lon lines, Loran TD lines, and your points.  You can, however, display your points on Google Earth (even with Loran lines).  One other consideration is that it only uses the WGS 84 datum.  Most GPSs come set up with this datum or can be set to it.  Different datums use somewhat different Lat/Lon numbers for the same spot.  Lastly, it dors not have ASF tables for non-USA areas.  This means that, if you are converting Loran numbers,  you will need to calibrate the program for your fishing area by giving the program some known Loran and GPS for some locations in your fishing area.  Alternatively, if you have already figured the appropriate offsets, you can enter them directly in the program.   Converting from one GPS brand to another is not an issue as this works everywhere as long as both are using the same datum. 

My program does not run, what do I do?
If your computer is running Vista or later and it gives an error message on the opening screen that says a needed file is not registered properly, then the User Access Control (UAC) may be an issue. First, try right mouse clicking on the program icon and picking “Run as Administrator”. The next time you run the program it will probably work without this step. However, there are cases where even this is not enough. For instructions on how to turn off UAC, click here. I suggest the Control Panel method for non skilled users. This UAC control is the pesky dialog that keeps asking you if it is OK to continue to run or install a program. It is intended to keep you safer from malicious software. You can try turning it back on after the problem has been fixed to see if it will live with this program.
With a download install, you will get a dialog with the message: “Enter the access code”.  Just  enter the access code that can be found in the e-mail sent to you when you ordered.  If it was a CD install, and you get the message: “The User Preferences file is damaged or missing…” ,  then a needed file called “UserPreferences.ini” is probably missing. You probably pulled the CD out prematurely.  A copy of this file is sent on the CD. This file does not get installed with the program, but is fetched when the program first runs. Therefore the CD must be in the drive or you must copy the file from the CD to the LoranGPS folder before you first try to run the program.  If you are upgrading, then you can copy this file from your old installation, if needed.   This file is not meant to be opened by you but by the program. It simply needs to be resident in the program folder when the program runs.

If the program has been running for a while but now gets the message: “The User Preferences file is damaged or missing…” , then the file is probably corrupted and needs to be re-copied from the CD. If you can get there, there is a button on the Tools>UserPreferences menu to re-fetch the virgin UserPreferences file from the CD.  Otherwise, you can manually copy the file from the CD to the LoranGPS folder.
For any other problem, try an uninstall/re-install before calling.us.

What do I do about an error message saying WMM.DAT is out of date?
To correct the error upon starting the program which states “WARNING – Based upon you computer’s date, you need to update the Magnetic Variation file (WMM.dat)” please follow these instructions:

  1. Download the updated WMM.dat file by left clicking this link: WMM.zip
  2. Extract the file (WMM.dat) from the zipped folder
  3. Save the new WMM.dat file over the old WMM.dat file.  This file is located in the folder where your copy of the program is installed, normally C:\LoranGPS.  The program requires the file be named “WMM.dat” so don’t rename it.
Why doesn't my printer print all the grid lines?
A customer wrote: “If anyone calls you with problems printing the spreadsheets with the new HP Photosmart 6280, it’s the printer!!!!!!!!!!!!!!!!!!!!!!!  I printed the Andren program fine for years on my XP powered desktop. I reinstalled my old reliable HP 2575 and it prints the grid lines as it always did.  The HP C6280 would print the first 2” of the grid lines (only the first two columns) and stop.  All the remaining columns printed fine, but no grid lines.  I bought this C6280 for my new Vista powered laptop which does not like my old reliable HP 2575.  The result with the C6280 was the same for the desktop and the laptop, no grid lines after the first two columns. If any of your other customers experience this problem with HP, I can recommend a Dell “All in One” 926 Printer.  I tested my son’s on my Vista powered laptop and it has no problem with grid lines!”
Another customer wrote: You can add the HP Photosmart 7280 All- In- One to this driver problem list.
My new laptop doesn't have a serial port, what now?
For track plotting or for uploading and downloading some older GPSs, a serial cable is needed. New laptop computers are usually without a serial port for connecting to peripherals like a GPS. They do have two or more USB ports and you will need to purchase a USB to Serial converter in order to connect to devices that only work with the standard RS-232 serial port. Converting USB to  RS-232 serial is not just a rewiring issue. Alternatively, if you have a Garmin GPS with a USB connection, the Garmin upload/downloader will handle the connection with USB only.
And, if you have a GPS with a memory card and a computer with a card reader you may be able to import/export the card’s file format. That way, you do not need a cable at all.
Note: If the COM port number set by Windows is out of the range handled by the uploader/downloader you are using, then do the following:
1. Open the Windows Device Manager. In XP: Right click My Computer Icon–Properties–Hardware–Device Manager
2. Right click on the COM port you want to change.
3. Left click on Properties.
4. Click on the Port Settings tab.
5. Click on the Advanced… button.
6. Use the drop down list to select the COM port number you want to use.
7. Click OK.
8. Click on OK again and close Device Manager.
Click here to see a screen capture of this process
What are the program's Import/Export Capabilities?
The file structure used by the SeaMarks program is based on dBASE III which is a very widely recognized data base structure. This program, however, is not tolerant of variations in the file structure. If you have a data base of waypoints in some other form and want to import it into the SeaMarks program use the built-in import routines described here or use the EXCEL technique described at the end of this section. If you can restructure your file to have the SeaMarks dBASE structure, then use the normal File_Open routine.

In Version 7.0 three more fields were added to improve the ability to handle data imported from GPSs. Older versions of the SeaMarks program that use DOS have a different file structure but it is recognized by the normal File_Open routine. Earlier version files will be automatically updated for the Name, Depth, and Icon fields as they are opened for the first time.
If you have a Garmin, Lowrance, Eagle, Furuno, Magellan, NorthStar, Sea-Nav, Simrad, or Raymarine GPS, you should be able to use the built-in upload/download or import/export capability of the program in lieu of using another program to upload and download the GPS. Most new GPSs have the ability to load and save the waypoints as files onto a memory card of the SD and CF varieties. The program has import/export utilities to handle most of these files. The following list shows the GPS track Plotters known to be compatible with this program.

GPS Track Plotters:
C-Map XML or userimg.bin for any GPS that uses C-Map cards
Eagle USR
Furuno GP30, 32, 33, 37 serial cable connection
Furuno DMX
Furuno NavNet RAT/ROU, PNT, or BIN
Furuno NavNet-3D CSV
Furuno Time Zero TZD
Garmin serial cable connection
Garmin/Mapsource GDB or MPS
Humminbird HWR
Lowrance USR, WS1
Northstar NMEA NTI or userimg.bin
Northstar 941 series serial cable connection
Northstar M series
Raytheon NMEA WPL
Raymarine archive.fsh
Raymarine TXT
Raymarine Waypoint File RWF
Simrad userimg.bin
Simrad USR, XML
Sitex userimg.bin
Standard Horizon NMEA WPL
Using this capability, you can move your waypoints between brands and models when upgrading your GPS. An attempt is made to match Icons between brands, but this cannot be guaranteed.
If, however, you are trying to work with another program or data source to import or export data, this list shows other the programs that handle waypoints and that the SeaMarks program can exchange data with.

Programs and file types
ASCII (pure text in CSV format) with selectable fields
C-Map PC Planner
Garmin PCX5
Humminbird PC
Loran Locator LX or AX
Lowrance GDM6, LS1
MaxSea (for Furuno)
MPS, GDB for Garmin mapsource or HomePort
Maptech marks.rec or mark32.txt
Nobeltec ONF
Northstar WinDBLoad
Offshore Hunter text export
Ozi-Explorer DMX
P-SEA WindPlot
Raytech Navigator
and others; using GPS Babel

Download the manual and read chapters VI.6.6 through VI.6.12 for a detailed look at these routines.

The SeaMarks program will export files which can be imported by the routines listed above. It will export NMEA in only the Raytheon and NorthStar varieties.
In all the exports that target loading waypoints into a GPS, an Export Options dialog comes up to help you select what is to be exported. The first choice is how many waypoints to export assuming that the file has more than the GPS can hold and the second is whether or not to include the reference Inlet.

For Garmin/Mapsource exporting, assuming you don’t want to use the cable upload/download capability, you would use the userdata.adm, GDB, MPS, or GPX capability. The Garmin software will alphabetically sort your file and will reject any duplicated names.
For Eagle/Lowrance if you do not use the cable uploading capability, you can create USR files to write to an SD card.

Excel can open the dBase files native to the SeaMarks program.  Excel 2007 versions and beyond can not save dBase files, so they cannot be used to send data directly to SeaMarks.  However all versions of Excel can take SeaMarks files and convert them to another form such as CSV that can be readily imported.

The program comes with many capable importing routines, but it can’t handle all possible situations.  Microsoft’s EXCEL is an excellent tool for importing and exporting between the program and arbitrary text and formatted files like found on the Internet.  What you need to do in Excel is reformat the information into the right sort of data and save the file as “CSV (comma delimited) (*.CSV)”.  If the description fields have commas then replace them with something else like dashes.  Having extra commas in a CSV file will cause the waypoint to be read incorrectly.   The steps are as follows:

1. Open the source data in Excel
2. Start by making sure the latitude and longitude data is in the right format.  Some data on the Internet separates the E/W and N/S indicators and/or the degree and minute data into different columns.  It is necessary for the numeric data (degrees and minutes) be in one column for each of latitude and longitude.  The acceptable formats for Lat/Lon are listed elsewhere in this document.  If the degree and minute data is in separate columns, that needs to be fixed.  One way to accomplish this is to create two new columns and fill them with the degree data plus the minute data divided by 60.  The E/W and N/S stuff is not necessary, so if it is in separate columns, that is no problem.
3. Do a global search and replace of all commas with semicolons.  Extra commas will make the file get read incorrectly, that is, it can shift some of the data into the wrong fields.
4. Save the file as “CSV (comma delimited) (*.CSV)” by setting this type in the Files-Of-Type box that is part of the Save-As dialog.
5. Then, with the SeaMarks program open, go to tools>Import Waypoints>Text, comma delimited.  Ignore the file already loaded as that will be dumped from memory once the import takes place.
6. You will get a new dialog to specify the fields to be imported.
7. If the data was loran and the Lat/Lon fields (or TD fields) are zero or wrong, don’t worry, you can calculate the Lat/Lon (or TDs) using Tools>Recalculate Lat/Lon  (or Tools>Convert File) later.
8. Make sure the center Lat & Lon, Inlet name, and Inlet Lat/Lon are right in the file by examining File>File Properties.  If they are not right for the data you are importing, fix them.
9. Save the file, giving it a new name if desired.

One caution on using Excel.  It is not a data base program, so it does not maintain the rows of the spreadsheet as records.. That is, if you don’t select all columns when doing a sort, you can destroy the data integrity.  If you sort only the latitude column, but not the rest of the data, that makes the waypoints useless.   

Where can I get NOAA (BSB) charts?
SeaMarks, handles the BSB/KAP and NOS/GEO forms of NOAA charts. Each order will come with a free region of BSB NOAA charts as appropriate. That is, for the apparent section of coastline you are closest to.  If you are in the center of the state of in some other non coastal state like North Dakota, then be sure to inform us of where you fish when ordering. If you want other NOAA charts besides the ones shipped or can’t wait for the CD, you can go nauticalcharts.noaa.gov  to get the charts you need. For some non US areas you can buy charts from: sea-tech.com .  These cover the Bahamas, central America and the Northern part of South america as well as New Zeeland.  You can check 1yachtua.comp for BSB charts for Europe and other popular cruising areas.  Try also, openseachart.org and look for BSB/KAP charts.  They have some free ones for South america.  If you know of another source of charts for non-USA areas, please let us know.
Where can I get 2D Bathymetric (NOS) charts?
Each order will come with a free region of 2-D bathy charts as appropriate and if available. You can get additional bathy charts for free from: ngdc.noaa.govl . However, these, while the same or improved charts from the ones previously seen here, are a slightly different format and not compatible with the program. You can view them instead with a free:MrSidViewer. The capability to work with these charts in the program is not anticipated However, while they are good for identifying good areas to explore, they are cluttered with so many lines that they tend to obscure the waypoints. For that reason, I generally tend to use the simple charts for my own book.