Opening and Displaying SRTM (hgt) data in Rhino

My goal is to be able to open and view SRTM data in Rhino.

I am attempting (new user) to create a script file in Grasshopper using ELK to display SRTM (.hgt) data in Rhino

Attached is a screen shot of my attempt.

Any input would be appreciated. Does anyone have a generic script file for opening SRTM data that they would be willing to share?

Is there a command / trick to view the data in rhino once the script file is complete?

Thank you

Replies to This Discussion

Permalink Reply by Timothy Logan on April 22, 2016 at 8:18am

You need to define what the domain is for the latitude and longitude.

If you want the entire tile, just set it to whatever domain is specified in the Info output. I would recommend you turn the preview off of the topography component if you're doing a large set and then just look at the data you want. even a 1 arc second file is going to have almost 13 million points in it and it takes forever to render. Just looking at the surface should be pretty quick though.

If you're wanting just a portion of the tile, just adjust the domain to only pull what you want, say "-71.8 To -71.4" and "44.2 To 44.6" or something like that.

Permalink Reply by Dylan Burns on April 27, 2016 at 6:51am

Thank you for the Reply.

I tried to implement your suggestions, but I am still having issues. I get the following error:

"1. Solution exception:Index was out of range. Must be non-negative and less than the size of the collection.
Parameter name: index"

Also I am still unable to view anything in Rhino. (Is there a step I am missing in order to visualize the data like you showed in your image?)

I have attached my .gh file to this as well

Thank you again for your help.

Attachments:

hgt input.JPG, 42 KB
hgt input.gh, 7 KB

Permalink Reply by Timothy Logan on April 27, 2016 at 7:19am

The exception your getting is usually related to the domains deviating beyond the bounds of the tile, though your domains are certainly not doing that. Because you're getting an error, it never finishes solving for the topo so there's nothing to display in Rhino.

Your file works fine when I download it and plug my own HGT file into it (same tile). When did you download/install Elk? There were some significant problems that you could run into with the older versions.

Permalink Reply by Dylan Burns on April 27, 2016 at 7:46am

I downloaded Elk and Grasshopper about 2 weeks ago.

I have Rhino Version 5 SR12 64-bit

Grasshopper Version August-27, 2014 Build 0.9.0076

ELK I believe was 2.2.2

Even when I attempt to open example .gh files that are supposed to have visual displays in rhino I do not see anything...

Permalink Reply by Timothy Logan on April 27, 2016 at 7:52am

For display, there are some settings that you can turn on/off that affect how things are displayed or not displayed. Look at the buttons on the right side of the GH window in the bar between the canvas and the ribbon.

Permalink Reply by Dylan Burns on April 27, 2016 at 8:35am

Yes, I do have those display buttons turned on.

What version of Rhino, Grasshopper and Elk are you running? (If you are able to open the .hgt file and visualize using my script, maybe I will try to use the same combination of versions as you)

Thank you!

Permalink Reply by Timothy Logan on April 27, 2016 at 8:57am

I'm running the same as you. Rhino 5 SR12 64bit, GH 0.9.0076, and Elk 2.2.2.

Permalink Reply by Dylan Burns on April 27, 2016 at 10:50am

Thank you for all your help.

I am still at a loss as to why I can not see anything displayed in Rhino.

I modified the .gh file slightly and was able to eliminate the Solution exception error (by switching the min and max values for the longitudinal domain)

I have attached:

1.) my update .gh file,

2.) a screen shot of GH and Rhino(with nothing displayed)

3.) The .hgt file I am using

Attachments:

Permalink Reply by Timothy Logan on April 27, 2016 at 1:25pm

Alright, tracked down where the problem is, but it may be a couple of days before I can fix it and get it uploaded. The problem is when it's reading the HGT file, there's one part that's hard coded to assume a 1 arcsecond file, and what you're using is 3 arcseconds. The quickest solution until I can push out an update is to use the higher resolution file for now.

Permalink Reply by Dylan Burns on April 28, 2016 at 8:41am

Thank you for tracking down the issue. I did try 1 arcsecond file, and was still not able to view anything in Rhino.

Where did you get the .hgt file you used that worked and gave you a visual display in Rhino?

"Alright, tracked down where the problem is, but it may be a couple of days before I can fix it and get it uploaded. The problem is when it's reading the HGT file, there's one part that's hard coded to assume a 1 arcsecond file, and what you're using is 3 arcseconds. The quickest solution until I can push out an update is to use the higher resolution file for now."

Permalink Reply by Timothy Logan on April 28, 2016 at 10:32am

I usually get HGT files from here:

http://dds.cr.usgs.gov/srtm/version2_1/SRTM1/

Alternatively you can use a GeoTiff or IMG file. For GeoTiff's I usually go to Earth Explorer, and for IMG files I usually go to the National Map Viewer.

I try to go fairly in-depth on the sources and types of files i use here https://vimeo.com/143013822

Permalink Reply by Dylan Burns on April 28, 2016 at 10:51am

Thank you. I just downloaded the higher resolution HGT files from:

http://dds.cr.usgs.gov/srtm/version2_1/SRTM1/

I started from scratch on the Grasshopper script file and still am unable to view anything in Rhino. (see attached)