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X and Y Offset in SRTM height data. (shifted data)

Markus Gpsmax shared this problem 16 months ago
Closed

Hello

I exported all my Data with one GIS-Software. (GlobalMapper)

I had 1 height-Data Layer, out of it i created a raster-Map (Hillshade)

Then i exported both with same Projection. (both layers fit perfect in Global-Mapper)

But: on Locus my Height-Data is shifted some meters to top and left.

My Raster-Map exactly fits to Lo-Maps.

Comments (7)

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1

Dear Markus,

I'm sorry but I'm not familiar with GlobalMapper. I'm not sure if I understand how you exported the map and hgt in the same projection. However it seems that you're able to export HGT file properly from GlobalMapper (based on second topic). So would you please export elevation data in the same way as you described in https://help.locusmap.eu/topic/srtm-hgt-file-handling

Thanks, Petr

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Hello Petr

yes, this data is also shifted. So because locus exactly fits my Raster-Map to the LoMap-Vector map i think my projection is also OK. just locus "displays" the .hgt height data shifted some meters to top and left.

The resulting problem is now that, when i plan a Route along a street (automatic Route calculation) normally the road is smooth. but now the height data is shifted so that locus pics heights that are in real some meters beside the road, and sometimes there are waterways beside my road, so i get a rough "untrue" height profile.

So i opend a new Topic..

My first thaughts are: Locus uses not enough coordinate decimal digits or the top-left starting is fit wrang.

The thing is, when i open my .hgt file in other Gis-Software it fits perfect to my other Data. just in locus not.

Can you check if locus uses same digits after decimal-point like locus uses for maps ?

Can you check if locus fits top-left edge exact ? i mean if there is a problem with zero or 1, or so.

thanks, Markus

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Hello Markus,

I hoped it will be a problem that may solve Petr (as a person who takes care of our database of HGT files), but seems it have to be some problem in the app.

It is possible to share with us one problematic file together with coordinates where this is most visible? Thanks

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Yes, sure. OK, if you want to check it also in Locus, i have to share whole N47E009.hgt and a part of my Raster-Map (i make this smaller to save Space)

Then I send you some Screenshots here also.

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Hello

I checked again my Data. There is all OK.

But still i see a Shift on Locus-Map


So here is a Link to download my Data.

https://drive.google.com/drive/folders/1dN4MZKXMSDdzqej9l6_Ku2e8C7hZY2lL?usp=sharing

If you can´t Access it, please give me a Feedback. (i didn´t try out)

I give u a coordinate, where you see it best later

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Hello

Here some Screenshots.

And at following coordinates you can test it for yourself: N 47°15.858' , E 009°41.580'


My idea is:

N47E009 is the Coordinate for the center of the buttom left "pixel". So for my Resolution of 0.125" its +0.0625 from buttom left "pixel" edge.


And maybe you did this Calculation for x double times and not for y ?? (Didn`t change variable after copying a programm line?)

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Hello Markus,

seems we have moved to a different topic here https://help.locusmap.eu/topic/srtm-hgt-file-handling , so I close this one to keep the discussion on one place. Thanks for understanding.

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