Conversion service

We can convert your Loran data to GPS for you using the SeaMarks program.  Or we can convert your file of points from one brand of GPS to a file of points for a different brand.  

The cost of the conversion service is dependent on the work involved. If the list of points is supplied in an electronic form that can copied and pasted, then it is $30 regardless of the number of points. If it has to be typed in, then it is $30 setup plus $30 per 60 waypoints or fraction thereof. Other charges may occur if a supplied list has significant differences from the suggested format and needs additional work.

The accuracy of Loran to GPS conversion is dependent on the accuracy of the ASF tables. In many areas, that means about 250 ft accuracy. In some areas, the tables have been calibrated with data given us by customers, so you will get better accuracy. If you can provide calibration data, then the accuracy can be improved further to almost that of Loran. That calibration data would be pairs of Loran and GPS measured data in the same area as the points to be converted. Processing the calibration data would be free as it benefits any future customer who needs conversions in the same area.

All waypoint data received is treated as secret. Calibration data is used to calibrate the ASF tables, but the raw data itself is never disclosed.

The preferred form of Loran data needed is a comma delimited pure text list like:

27429.1, 43867.5, Nameless, NEW LEDGE PAULS REEF
27362.9, 43707.8, PHONY, PHONY LEDGE
27362.5, 43913.2, 0003, PONY LEDGE NORTH
27348.0, 43701.6, 0004, NON EXISTENT REEF

This is a file with four fields: TD1, TD2, NAME, and DESCRIPTION. If you want more fields in the list, like depth, group, icon, color, or rating then you can add them too. The available fields for SeaMarks are: Name, Loran TDs, Lat/Lon, Rating, Description, Color, Date, Comments, Icon, Depth, and Group.  Your data will be fit into the appropriate fields.  If you have some data that does not fit one of these fields, it will be placed in Comments.  The minimum number of fields is 2: TD1 and TD2. Just make sure that, however many fields there are in the list, there are one fewer commas (no more, no less). All rows of the list should have the same number of fields (and commas). If any field data is missing, just leave it blank, but include the appropriate commas. Please do not put blank lines between the rows, have only one waypoint per row, and do not format into pages.  Make sure you do not have commas within the text fields (extra commas) unless the text filed is enclosed with quotation marks.

Loran C numbers are always 5 digits, a decimal point and 1 or 2 more digits. If the number has more than 5 digits before the decimal point, we will assume that you forgot the decimal point and it will be divided by 10 repeatedly until the decimal point is in the right place. When we convert the file, we sometimes find that some of the points are way apart from the rest, indicating major typing errors.  We will email you for the correct numbers.  We cannot find or correct minor typing errors.

The various fields in the SeaMarks spreadsheet are:  

  • Name:  From 6 to 16 characters and intended as the Name in your GPS display.  All names should be unique and not longer than your GPS allows
  • Loran TDs:  5 digits, a decimal point plus 1 or 2 more digits
  • Latitude: In one of the forms DD.DDDDD, DD MM.MMM, DD MM SS.S .  Negative if South
  • Longitude: like Latitude with possibly one more D.  negative if East (can be set positive East)
  • Rating: 4 characters describing how good the spot is.  Generally not used in  a GPS.
  • Description: 32 characters.  This might go into your GPS as a description
  • Color: The leading character of the color.  Choices are Blue, Green, Cyan, Red, Magenta, Yellow, Orange.  Use lower case for light, upper case for dark and a blank for Black.
  • Date:   Some standard form
  • Comments:   90 characters used for whatever.  This will probably not have a place in your GPS
  • Icon:  up to 12 characters.  Will be matched to the set: X, O, square, triangle. diamond, box, checkout, skullXbones, warning, hardbottom, ledge, rocks, reef, mark, bouy, anchor, wreck, smwreck, NOAAwreck, swim, tree, weed, diver, dive flag, smfish, fish, 1fish, 2fish, lobster, restricted, gas, ramp, pier, oil rig, bait show, ?.
  • Depth:  6 characters numbers and text.   Like 62ft.
  • Group: 16 characters intended for those GPSs that allow formation of groups

The list can be embedded in an email or in a text file or spreadsheet attached to an email. If you mail or FAX a hand written or typed list, then the higher cost applies as we will need to type it into the computer. We also need an initial idea of the location of the points to be converted. It should be within 50 miles of the points to be converted. That would be like: 28 06.0N, 80 13.0W for offshore Melbourne Florida.  The name of your inlet or coastal city would also work.

An Excel spreadsheet is also OK as an alternative. It should have the data in columns, TDs in adjacent columns, one waypoint per row, no blank rows, and no commas.

You will get an email with the converted data and a picture of a chart showing how your points lie. If you want a file that you can put onto a card to put into your GPS and load in the data, let us know. Indicate what brand and model GPS you have. That costs $10 more if added onto a Loran to GPS conversion or just $30 for a GPS to GPS conversion.

If you mail in the points and don’t have an email address, then you will get back a printed list of points and a printed graphic. If you want the extra file to put into your GPS, then you must send the card along with your list or buy one from us.  SD or CF cards with shipping are $10 more.