How to use *.NUM file containing info about a digital elevation raster?

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06-24-2021 10:15 AM
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CarolRichards
New Contributor II

Hello,  I'm using NASA digital elevation raster files (file extension *.hgt from the NASA DEM) in ArcGIS Pro.  NASA provides an additional *.NUM file containing information which identifies the data source for each raster cell.  NASA describes this as a scene layer.  I want to read this NUM data into ArcGIS and analyse it (e.g. using the reclassify tool) so I can visualise the sources of data. 

The problem: I can't figure out how to bring the *.NUM data into ArcGIS.  I've tried searching for guidance in the ArcGIS Pro user help and searching the internet, however can't find a solution or information on how to pre-process the file.  I've also tried using Toolbox tools (such as the Binary to Raster tool), however ArcGIS doesn't seem to recognise the NUM file type.  Does any one know a way to bring this type of data into ArcGIS Pro?  Or what pre-processing steps are needed?  The attached image shows how the files appear (unfortunately their size is too large to attach to this post).  This is what NASA says about the files.

I hope you can help, or share any ideas... I can't think what else to try!

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CarolRichards
New Contributor II

Hi Dan,

Great idea!   I tried changing the file extension to *.img and *.tiff, for which ArcGIS returned an 'unsupported data type' error when trying to open the file.  However, still feeling hopeful I decided to work down the full list of ArcGIS Pro raster file types (shared in Robert's post), trying many of the file extension types.  Great news, changing to the *.raw extension type has enabled Pro to read the data.  Fabulous!  Thank you for your idea Dan; I really appreciate the expertise you've shared. 

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DanPatterson
MVP Esteemed Contributor

have you confirmed it isn't a text file? (try opening in Notepad or other text editor)

The NUM layer indicates the number of scenes that were processed for each pixel and the source of the data. 


... sort of retired...
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CarolRichards
New Contributor II

Hi Dan, thank you for your reply & suggestion.  Yes, I've tried taking a look in Notepad; the data appears as unintelligible text characters.  I've also tried different ways of importing the file into Excel, but it displays the same unintelligible characters.  Still at a loss to understand what encoding format the data is in!   

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Robert_LeClair
Esri Frequent Contributor

I checked the Data Interoperability extension and the NUM file is not listed there.  HGT is a supported raster format for ArcGIS based upon this link here

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CarolRichards
New Contributor II

Hi Robert, thank you for checking the compatibility of the NUM file type and replying.  So the NUM file sounds like it needs some kind of transformation outside of ArcGIS first.  Any thoughts on what I could try to do this?  I've never come across a NUM file before and I can't see anyone else talking about it on the internet or stackexchange forums.  Yes, no problem using the HGT raster :beaming_face_with_smiling_eyes:.  

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DanPatterson
MVP Esteemed Contributor

from The Shuttle Radar Topography Mission (SRTM) Collection User Guide (usgs.gov)

on a lark... try renaming the "num" file with a *.img file extension and see if it loads.  The code for deciphering what each pixel means is in that document.

I can't find any direct readers but renaming with a readable extension is worth a try


... sort of retired...
CarolRichards
New Contributor II

Hi Dan,

Great idea!   I tried changing the file extension to *.img and *.tiff, for which ArcGIS returned an 'unsupported data type' error when trying to open the file.  However, still feeling hopeful I decided to work down the full list of ArcGIS Pro raster file types (shared in Robert's post), trying many of the file extension types.  Great news, changing to the *.raw extension type has enabled Pro to read the data.  Fabulous!  Thank you for your idea Dan; I really appreciate the expertise you've shared. 

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DanPatterson
MVP Esteemed Contributor

No problem, glad it worked out


... sort of retired...
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