Thread: Creating my own JNX map for Etrex 20

Thanks for the comments Giomen. I think I have solved my calibration problem.

In MAPC2MAPC my work flow is as follows (using the Wizard interface):
Load an Image File and Calibrate it
Calibrate with Map Coordinates
Then my error. I was using Latititude Longitude /WGS84 for calibration. --- and using the Lat/Long figures printed on the map corners.

I have changed this to Other Grid and Selected Nepal ---- duh! obvious I guess.

So instead of working with the Lat/Long of the corners I am working with the map grid coordinates.
Results viewed in Google Earth align well with the Google Earth image detail.

Test map Kathmandu.kmz is here

Code:

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Next I have to crop the borders from my map set in Photoshop.
Problem -- the map border is not quite square to the map grid. The border is aligned on the Lat/Long lines.
So I think I will have to warp the map in Photoshop to make the borders rectilinear, so then I can crop the image with the Photoshop crop tool and hopefully the calibration will still work.

When it comes to setting the JNX scale I have read elsewhere on this site:

JNX format description contains the following "standard" set of scale values, which is recommended to use in the hand-made JNX maps: 75, 149, 298, 597, 1194, 2388, 4777, 9554, 19109, 38218, 76437, 152877, 305758, 611526, 1223072, 2446184.

This set is an extension of the set used in BirdsEye subscription maps: 597, 1194, 4777 and 76437.
Still, there were no explanation of what these numbers mean.

Is there any clue to how these relate to display scale distances as seen on the Etrex screen?
I have found that using a JNXScale of 2388 makes the map appear when the 800m scale is visible on the Etrex and when the 1km scale is visible in Basecamp.