Converting Lowrance Sonar Viewer Output Files

[quigley595]

Hi folks,
For those of you that use the Lowrance Sonar Viewer software, this might be of interest, for anyone else, this will be just a long boring post, so I wouldn't read any further.

I have worked out how to convert the Latitude & Longitude figures from Sonar Viewer, back into real Lat & Long.

When you log sonar data in the Lowrance and save it to your SD card, you can use the Lowrance Sonar Viewer software to look at it on your PC.
This software also allows you to output the sonar data to a file (a CSV file).
Problem is the Lat and Long are expressed in Lowrance Mercator Metres, eg -3093277, 16987095 in the Lowrance file is really -26.841499, 153.111022. in real Lat / Long.

Note that there is a short and a long method for this conversion. The short one is simple, but results in an error of about 2 metres, due to the rounding and complexity limitations on formulae in MS Excel.
I will describe the short version.... If you want the long one, let me know.

HERE GOES This is how you convert the Lowrance figures.

0. Log your sonar data in the Lowrance combo when you are out on the water, then save it to your SD card in the unit when you are back at the boat ramp.
1. Back at your PC, load the file from the SD card into Sonar Viewer program.
2. Click on File->Output Chart Information to save it to your PC in CSV format. (NOTE... I found that I had to save it in TXT format, as the CSV format didn't work for me. The TXT format still saves it as a CSV file).
3. Open MS Excel and load the CSV file
4. Look at column N and O... they have the titles "Position X" and "Position Y". These correspond to the Long and Lat respectively.
5. Insert 2 blank colums just before colum N ("Position X" will now be Col P and "Position Y" will now be Col Q)
6. In Cell N1 enter the phrase Long (this is the longitude), and in Cell O1 enter the phrase Lat (this is the latitude)
7. HERE COMES THE HARD BIT.....
8. In the Cell N2, enter the following EXACTLY: =(P2/6356752.314)*57.29577951
8. In the Cell O2, enter the following EXACTLY:
=((2*ATAN(EXP((Q2/6356752.314)))) - 1.570796) * 57.29577951

9. Copy these 2 cells all the way down to the bottom of your file.
10. Thats it done!.

You will notice that many of the Lat / Long figures are Zero... this is because the Lowrance Position X and Position Y are zero (the "Position Valid" (Column N), for these cells will be "F" for false. I dont know why this is.. maybe someone can explain it to me.

Thats it... you can now cut out the rows and columns you dont need and import the good data into some other charting software you may use, or Google Earth etc....

Works for me!

I dont know if I can attach a sample Excel file on here... if I can, someone can let me know how to do it.

regards
Mike

[frankj]

Mike,

Good stuff.

I'm fairly sure the reason you get the zero's in the position column is because the track updates only occur at certain intervals, which are presettable by the user.
The sonar pings are occurring at a much faster rate that the track updates, thus the blanks in the position entriy columns.

e.g. ping, ping, ping, ping, ping, ping,trackpoint-ping, ping, ping, ping, ping, ping,trackpoint-ping, ping, ping, ping, ping, ping,trackpoint, etc.

Clear as mud.

Cheers
Frank

[HSetiawan]

Hi Mike,

Is it possible to post the long version please?
I need to convert my readings to a high accuracy coordinates so eliminating the 2 meter shift is crucial for me.

Cheers,
Hery