[Redwulf__32]

Still working on my Denmark map. Not satisfied with the STRM3 (relativly coarse) coastlines using MicroDem, I'm currently fixing them up Google maps as a reference (scaling a 2 km Google maps by 0.4255 and superimposing it over the original STRM3 map puts you in tha ballpark). Results are stunning, very detailed and realistic coastlines, lakes and rivers are possible. However, since Google maps uses a Mercator projection the vertical distortion is clearly visible when comparing to my STRM3 based map_c, the Denmark map being quite large.

I've used WDS 1984 Datum in MicroDem, could this be the problem (not being a cartographer)? Is it possible to do a Mercator projection in MicroDem (which would be ok for an IL2 map) or do I have to write a projection application to convert a WDS 1984 map to Mercator projection (not that I mind doing so, always love a good challenge) 8)

All help most welcome.

[delvpier]

Still working on my Denmark map. Not satisfied with the STRM3 coastlines using MicroDem, I'm currently fixing up the coastlines using Google maps as a reference. Results are stunning, very detailed and realistic coastlines, lakes and rivers are possible. However, since Google maps uses a Mercator projection the vertical distortion is clearly visible when comparing to my STRM3 based map_c, the Denmark map being quite large.

I've used WDS 1984 Datum in MicroDem, could this be the problem (not being a cartographer)? Is it possible to do a Mercator projection in MicroDem (which would be ok for an IL2 map)

All help most welcome.

Since a few months, they updated STRM data files to version 4, and now when merging, i use only NAD84

For coastlines, I used HGT files to make some maps Sinai, Hokkaido, Egypt... and I found that I got a better result with coasts...

Link for HGT : ftp://e0srp01u.ecs.nasa.gov/srtm/version2/SRTM3

Link for STRM4 :http://srtm.csi.cgiar.org/SELECTION/inputCoord.asp

[Redwulf__32]

Still working on my Denmark map. Not satisfied with the STRM3 coastlines using MicroDem, I'm currently fixing up the coastlines using Google maps as a reference. Results are stunning, very detailed and realistic coastlines, lakes and rivers are possible. However, since Google maps uses a Mercator projection the vertical distortion is clearly visible when comparing to my STRM3 based map_c, the Denmark map being quite large.

I've used WDS 1984 Datum in MicroDem, could this be the problem (not being a cartographer)? Is it possible to do a Mercator projection in MicroDem (which would be ok for an IL2 map)

All help most welcome.

Since a few months, they updated STRM data files to version 4, and now when merging, i use only NAD84

For coastlines, I used HGT files to make some maps Sinai, Hokkaido, Egypt... and I found that I got a better result with coasts...

Link for HGT : ftp://e0srp01u.ecs.nasa.gov/srtm/version2/SRTM3

Link for STRM4 :http://srtm.csi.cgiar.org/SELECTION/inputCoord.asp

Thnx Delvpier, you are "Da Man"

I'll have a look, thnx once again.

[delvpier]

... you are "Da Man"

Well... certainly not !...only one amongst all others

All I known comes mostly from reading other posts... since last year :wink:

[fly_zo]

... you are "Da Man"

Well... certainly not !...only one amongst all others

All I known comes mostly from reading other posts... since last year :wink:

nevertheless , what you're doing is most appreciated ....

Z

[fabianfred]

I've just realised that I've been using the HGT files for everything.... :oops:

[Tigre_dos_Pampas]

Google uses WGS-84 too... this is a geodetic system (someone call datum), not a projection.

I believe Il2 maps are not projected, but represented as a ellipsoid part (roughly saying, "as is") This is due when you flying earth is not plane, but curved as you flying above an sphere (or ellipsoid).

As real coordinates are not represented in IL2 maps, we can't determine what projection or datum this uses. But i believe earth's curvature is so exagerated in IL2 (you can see earth spherical at 5000 m for example, and this is not true).

[delvpier]

Google uses WGS-84 too... this is a geodetic system (someone call datum), not a projection.

I believe Il2 maps are not projected, but represented as a ellipsoid part (roughly saying, "as is") This is due when you flying earth is not plane, but curved as you flying above an sphere (or ellipsoid).

As real coordinates are not represented in IL2 maps, we can't determine what projection or datum this uses. But i believe earth's curvature is so exagerated in IL2 (you can see earth spherical at 5000 m for example, and this is not true).

Absolutely right !

Those kind of things would be more documented if someone could decompile the Java code and make it readable...

[Redwulf__32]

Google uses WGS-84 too... this is a geodetic system (someone call datum), not a projection.

I believe Il2 maps are not projected, but represented as a ellipsoid part (roughly saying, "as is") This is due when you flying earth is not plane, but curved as you flying above an sphere (or ellipsoid).

As real coordinates are not represented in IL2 maps, we can't determine what projection or datum this uses. But i believe earth's curvature is so exagerated in IL2 (you can see earth spherical at 5000 m for example, and this is not true).

Absolutely right !

Those kind of things would be more documented if someone could decompile the Java code and make it readable...

Having the complete source code would be nice 8) Many things could be rectified/brought up-to-date.
However, I doubt the IL2 engine does any projection calculations, my guess is it simply presents the map info on a flat world.

Regarding the "earth curvature" seen at higher altitudes, what you actually are seeing is the limit of your visibilty sphere (which is seen as a circular segment of the ground). You can see this phenomenon in real life on a hazy day at higher altitudes flying below the tropopause (the stratosphere is not hazy).

Thnx for clarifying my datum/projection confusion, now I know how to correct the coastlines so they'll fit on the HGT based maps.