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[Solved] Optimal way to store and use DEM data

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Nikkitta Nikkitta
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[Solved] Optimal way to store and use DEM data

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Hi,

I want to use ASTER GDEM v2 data for the whole world from local disk.
What is the best way and file format to store this data locally and use it with osgEarth?

Currently I'm using single GeoTIFF file for the whole world of SRTMv4.1 with *.ovr created.
It has size of 21 GB and it take some time to load in osgEarth even with cache enabled.

The way of storing data
ASTER source GeoTIFF data has size of 1.4 TB. So my guess is to:
1. Store down-scaled data for the whole world in 1 file for distant views of Earth.
2. Store detailed data for regions (like 5x5 degrees) in separate files, to load needed region when the camera is close to the ground.

This approach will allow me to copy only needed regions in case of installing my app on other PCs.
But I want to be sure that this is the correct idea. Do you have any objection?

DEM file formats
Another problem is that I'm not sure that I use optimal and fastest file format (GeoTIFF) for DEM.
Currently I'm using ECW (WGS84) to store imagery, and GeoTIFF to store DEM.
In GlobalMapper I've found DEM formats like DTED and others.
Which one is optimal for use with osgEarth and for my needs?
Best regards,
Nikita Petrov
gwaldron gwaldron
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Re: Optimal way to store and use DEM data

A couple things:

First, if you use a GeoTIFF directly, make sure it is projected and internally tiled, as detailed here:
http://docs.osgearth.org/en/latest/data.html#tips-for-preparing-your-own-data

If this is still not fast enough you may need to build a pre-tiled dataset using osgearth_package.

Glenn Waldron / Pelican Mapping
Nikkitta Nikkitta
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Re: Optimal way to store and use DEM data

Yes, I did all the steps from the manual for SRTM data. And I do know that I have an additional option of using osgearth_package, as a backup plan.

But but I want to gain a deeper understanding and my questions are:
1. Is it possible to store data in lots of files (like 5x5 degrees) without loosing performance? Or it is strongly recommended to use single file to get best performance?

2. What is the recommended DEM file format to use with osgEarth? Is it GeoTIFF or it is not so important?
Best regards,
Nikita Petrov
gwaldron gwaldron
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Re: Optimal way to store and use DEM data

Nikita,

Storing your elevation data in many files will slow the tile creation speed, but it will not affect rendering performance once the tiles are done loading.

GeoTIFF is the best format to use for elevation.
Glenn Waldron / Pelican Mapping
Nikkitta Nikkitta
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Re: Optimal way to store and use DEM data

Thanks a lot, Glenn!

I will try to work with that huge data in a few weeks.
Best regards,
Nikita Petrov
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