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Generating Offline maps - question about coordinates

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Generating Offline maps - question about coordinates Empty Generating Offline maps - question about coordinates

Post  kapiderm on Mon Jan 07, 2013 1:51 pm

Hi,

New user here, thanks for creating OruxMaps and providing it for free.

I have read the manuals, and it seems to me that the process of creating offline maps requires that the map be converted from its original datum/projection/coordinate system to WGS84/UTM - is this correct? If so, then presumably OruxMaps displays positional coordinates only and always as UTM?

To put the same question a different way: soviet military maps available online are calibrated as Pulkovo 1942 datum / Gauss-Krueger projected
coordinate system (= transverse mercator). Its sometimes useful to take coordinates from a "moving map" application such as OruxMaps and transfer them to a paper map - but this is only possible in this case if the "moving map" application can display G-K coordinates. As I understand it, the conversion process for OruxMaps would recast the map as WGS84/UTM, and the OruxMaps App would display UTM coordinates - Is this correct?

Sorry for asking a beginner/conceptual question, and thanks in advance for any help

kapiderm

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Generating Offline maps - question about coordinates Empty Re: Generating Offline maps - question about coordinates

Post  orux on Tue Jan 08, 2013 8:30 pm

kapiderm wrote:Hi,

New user here, thanks for creating OruxMaps and providing it for free.

I have read the manuals, and it seems to me that the process of creating offline maps requires that the map be converted from its original datum/projection/coordinate system to WGS84/UTM - is this correct? If so, then presumably OruxMaps displays positional coordinates only and always as UTM?

To put the same question a different way: soviet military maps available online are calibrated as Pulkovo 1942 datum / Gauss-Krueger projected
coordinate system (= transverse mercator). Its sometimes useful to take coordinates from a "moving map" application such as OruxMaps and transfer them to a paper map - but this is only possible in this case if the "moving map" application can display G-K coordinates. As I understand it, the conversion process for OruxMaps would recast the map as WGS84/UTM, and the OruxMaps App would display UTM coordinates - Is this correct?

Sorry for asking a beginner/conceptual question, and thanks in advance for any help

Hi;

You can use OruxMapsDesktop to convert maps from a lot of datums/projections (including Pulkovo 1942 datum and transverse mercator projection) to the format used by OruxMaps.

And you can display the coordinates in OruxMaps in different formats (UTM, geographical, MGRS, grid, ...) using different datums than WGS84.


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Generating Offline maps - question about coordinates Empty Re: Generating Offline maps - question about coordinates

Post  kapiderm on Wed Jan 09, 2013 2:25 pm

Hi - thanks for taking the time to reply, and also for producing the excellent app.

Good news that OruxMaps can display various coordinates - does that include Gauss-Kruger?

If not, does OruxMaps allow for a user to add other coordinate sets, say via an xml file?


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Generating Offline maps - question about coordinates Empty Re: Generating Offline maps - question about coordinates

Post  epic on Mon Jan 28, 2013 11:20 am

You may select to display the grid coordinate. If the projection of your map is Gauss-Kruger (TM),
then the grid coordinate is TM coordinate. However, I found a bug in the otrk2.xml for the TM
projection. When you define the TM projection in Oruxmaps desktop, you need to enter the Longitude
origin (central median) based on the datum you select, OruxMapsDesktop will translate the bounding
box to Lat/Lon in WGS84 as in otrk2.xml. However, for the TM to calculate correct grid corrdinate, the central median (as recorded in otrk2.xml) need to be translated to WGS84 too. But OruxMapsDesktop
simply copy the central median in your own datum to otrk2.xml, which is not correct.

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