Mix 1, 2, 5 metre elevation data in one mosaic dataset

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07-12-2017 10:54 PM
MarkMindlin
Occasional Contributor III

Hi,

I just hesitate if it is not wrong to mix (add) 1, 2, 5 metre elevation data *.asc in one mosaic dataset?

Any ideas?

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GünterDörffel
Occasional Contributor III

you have 🙂
In Catalog vue, AFTER you have added data, open the properties of the MosaicDataset.
The Default and General Tabs hold important settings. Go to General Tab - there is an editable property called  Cell Size

Now coming back to your multi-resolution data: If you set this property to 5,5 you will always have 5m resolution offered by the MD - even in areas where your data has 1m or 2m resolution.

You should also set the type of the MD from generic to elevation

that will make sure the stretching is Min-Max by default as appropriate for elevation.

And set the compression to LZW or LERC to reduce data transported ... 

And calculate statistics - very important for elevation. Have you converted the 'asc files to tiff?

Regards
Guenter

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GünterDörffel
Occasional Contributor III

Mark,

I do really like the idea of mosaic datasets ingesting any format "as is" and it will work for *.asc files. But as to my personal experience and tests done with *.asc delivered point data from a survey company, I'd convert the asc-files to some format that can be accessed in tiles and indexed properly. You SHOULD TAKE A LOOK AT THIS!

You can mix the resolutions - technically no problem. As long as you are aware what that means for your analysis:

  • Will lower resolution be something like "overviews" or will the areas have mixed resolution side-by-side?
  • Do you define the MosaicDataset resolution to be like the "workst" you have - downsampling the better resolution?
  • OR .. "upsample" the bad ones to give you "pseudo-resolution" in some areas?

Whenever there is coverage of multiple resolutions at one spot, the MosaicDataset can make sure to use the best resolution available, no concern there ...

Regards
Guenter

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MarkMindlin
Occasional Contributor III

Thanks Guenter,

There are side-by-side not overlapping areas.

It is an important point about downsampling/upsampling.

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MarkMindlin
Occasional Contributor III

Guenter,

How I set the MosaicDataset resolution? 

I have no such parametre when I create a MosaicDataset.

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GünterDörffel
Occasional Contributor III

you have 🙂
In Catalog vue, AFTER you have added data, open the properties of the MosaicDataset.
The Default and General Tabs hold important settings. Go to General Tab - there is an editable property called  Cell Size

Now coming back to your multi-resolution data: If you set this property to 5,5 you will always have 5m resolution offered by the MD - even in areas where your data has 1m or 2m resolution.

You should also set the type of the MD from generic to elevation

that will make sure the stretching is Min-Max by default as appropriate for elevation.

And set the compression to LZW or LERC to reduce data transported ... 

And calculate statistics - very important for elevation. Have you converted the 'asc files to tiff?

Regards
Guenter

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MarkMindlin
Occasional Contributor III

Many thanks, Guenter!

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MarkMindlin
Occasional Contributor III

Yes, I convert now to TIFF, add to MosaicDataset.

Should I change "Source Type" before or after I add the TIFF?

Should I do statistics at the time I add the TIFF to MosaicDataset? or after?

If a number of Bands is 1?

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GünterDörffel
Occasional Contributor III

The "Source Type" will not affect the loading process of the TIFFS but will change the initial display settings ArcMap applies - this is described here

The statistics can be done once you have added all data. If you have large single datasets without pyramids so far, use "Build Pyramids and Statistics" for the datasets (zhis will do for every single entry) and/or just "Calculate Statistics" for the whole MosaicDataset. Then things should look fine and behave as expected. If you have NoData - exclude it and recalculate the footprints to speed up the data.

And yes - Elevation should be one Band. Depending on the data it can be 16bit (integer) or 32bit (float)

Regards
Guenter

MarkMindlin
Occasional Contributor III

Thanks Guenter, appreciate your help!

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