Loran to GPS conversion service page

We will convert your loran data to GPS using the SeaMarks program.

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 conversion is dependent on the accuracy of the ASF tables. Normally, 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 kept confidential. Calibration data is used to calibrate the tables, but the data itself is never disclosed.


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


27429.1, 43867.5, 0001, 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
27344.4, 43877.5, 0005, LG BREAK FROM B.T.
27343.5, 43667.2, 0006, SM LEDGE
27342.4, 43742.0, 0007, SHOWS LOTS OF FISH
27341.1, 43833.2, Eagle, WHITE EAGLE LEDGE
27333.9, 43697.0, 0009, VERO SOUTH
27333.4, 43724.0, SPRING, FLOWING SPRING
27332.2, 43761.6, 0011, ROCK LEDGES


This is a file with four fields: TD1, TD2, NAME, DESCRIPTION. If you want more fields in the list, like depth, then you can add them too. The minimum number of fields is 2: TD1, 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, do not format into pages, and make sure you do not have commas within the text fields (extra commas).

Loran 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 a typing error. We will email you for the correct numbers.

The list can be embedded in an email or in a text file 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 lat/lon estimate 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.

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

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.

If you send 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.



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