Lisbon/Lisboa 1973 (DLx) Datum

Hello!

First I must say I love this app.

I would love it more if Lisbon/Lisboa 1937 (DLx) Datum was added to the datum list.

The military maps I have use that datum and the transverse mercator projection.

Eventhough the .map files say WGS84 it's not in WGS84 datum. I opened them in Global Mapper and it automatically detects WGS84, but then the gpx tracklog I recorded is about 200m away from where it should be. If I manually change the datum to Lisbon/Lisboa 1937 (DLx) it matches perfectly my tracklog.

Here you can find the transformation parameters to WGS84 datum (taken from global mapper website):

http://www.globalmapper.com/helpv11/datum_list.htm

I edited the datumsT.xml file and added this:

Code:

<TR><TD>Lisbon/Lisboa 1973 (DLx)</TD><TD>International 1924
</TD><TD>-289</TD><TD>-92</TD><TD>126
</TD><TD>Portugal</TD><TD>-1</TD><TD>-1
</TD><TD>-1</TD><TD>0</TD></TR>

The first 3 parameters (-289,-92,126) I got them from the global mapper table in the link above. I wasn't sure if it would accept decimals so I rounded it to the closest integer.

The last 4 parameters I wasn't sure what they were so I just copied the ones from the WGS84 entry (-1,-1,-1,0). What parameters are this and what should I put there?

Then I created maps with this datum and copied it to my android phone, and loaded it with the same tracklog I tested before and I got quite accurate results, not as accurate as in global mapper, but very very close (the small difference is probably due to the rounding in the parameters above).

If you need any more info or some sample maps/tracklogs just let me know.

Thank you,
Bruno

bgravato wrote:
The first 3 parameters (-289,-92,126) I got them from the global mapper table in the link above. I wasn't sure if it would accept decimals so I rounded it to the closest integer.

Hi, Bruno;

Current version uses Integers (I had not seen before values with decimals), but I have changed them for next version.

bgravato wrote:
The last 4 parameters I wasn't sure what they were so I just copied the ones from the WGS84 entry (-1,-1,-1,0). What parameters are this and what should I put there?

Not used; about accuracy calculations.

bgravato wrote:
Then I created maps with this datum and copied it to my android phone, and loaded it with the same tracklog I tested before and I got quite accurate results, not as accurate as in global mapper, but very very close (the small difference is probably due to the rounding in the parameters above).

Sure you are using UTM projection. Perhaps it is a Transverse Mercator projection with different parameters, not an UTM.

But do not worry; Of course that OruxMaps will give support to my neighbour country!

Send me a .map file -->oruxuro@gmail.com

orux

orux wrote:
Sure you are using UTM projection. Perhaps it is a Transverse Mercator projection with different parameters, not an UTM.

Yes, it uses Transverse Mercator. I tried to export using Irish Grid projection, which I believe is the same as transverse mercator, but the result seemed to be the same as using UTM.

But do not worry; Of course that OruxMaps will give support to my neighbour country!

Thank you

I'm sending you an email with map files and tracklog.

bgravato wrote:

orux wrote:
Sure you are using UTM projection. Perhaps it is a Transverse Mercator projection with different parameters, not an UTM.

Yes, it uses Transverse Mercator. I tried to export using Irish Grid projection, which I believe is the same as transverse mercator, but the result seemed to be the same as using UTM.

But do not worry; Of course that OruxMaps will give support to my neighbour country!

Thank you

I'm sending you an email with map files and tracklog.

Here is the difference:
Yours:
Projection Setup, 39.666666667, -8.131906111, 1.000000000, 200000.00, 300000.00,,,,,
RD (Transverse Mercator):
Projection Setup, 0, 5.3876333, 0.9999079, 155000, -5316592,,,,,

Each no UTM has its own parameters.

I will work with it soon,....

orux

Thank you

bgravato wrote:Thank you

This is a beta version that supports 'Transverse Mercator' maps:

http://rapidshare.com/files/354357792/OruxMapsDesktop1.4.0beta.zip

orux