topic How to Extract Height in meter using DSM? in Elevation Data Questions

How to Extract Height in meter using DSM?

AkhilChhibber1 — Thu, 15 Feb 2018 07:24:37 GMT

I want to get the height information for a particular area in meters.

I have orthomosaic, DSM and DTM of that area

I don't know how to get building height information that too particularly in meters.

I would be thankful to you for this help.

Re: How to Extract Height in meter using DSM?

JayantaPoddar — Thu, 15 Feb 2018 09:25:18 GMT

Aren't the pixel values of DSM and DTM the Elevation values in Meters?

If the values are in Meters, use Raster Calculator to get the difference of DSM and DTM as follows

"DSM_Raster" - "DTM_Raster"

If the inputs are Floating-point Rasters, then use the following expression

Float("DSM_Raster" - "DTM_Raster")

If you overlay the imagery on top of the the above resulting raster, the pixel values of the resulting DEM should give you the height of building in Meters. Results would be more accurate if the DSM and DTM are floating-point rasters.

Re: How to Extract Height in meter using DSM?

AkhilChhibber1 — Thu, 15 Feb 2018 09:47:11 GMT

I really appriate your help but could you please help me out regarding how to extract height using DSM as I am a bit new to Arcmap.

Re: How to Extract Height in meter using DSM?

JayantaPoddar — Thu, 15 Feb 2018 12:31:26 GMT

I have orthomosaic, DSM and DTM of that area

Considering you have all the above Rasters, did you get any error running Raster Calculator as I mentioned in my above comment?

Re: How to Extract Height in meter using DSM?

AkhilChhibber1 — Fri, 16 Feb 2018 06:39:13 GMT

Actually I don't know how to use raster calculator.

Can we derive the height only using DSM or we need both DTM and DSM????

Re: How to Extract Height in meter using DSM?

DanPatterson_Retired — Fri, 16 Feb 2018 06:58:17 GMT

raster calculator

have your raster layers in your data frame, launch the raster calculator.

In the picture in the link it shows how to add three rasters together.

subtraction is the same principle

double-click on the raster names and sincle click on the operator ( -) . Just get the rasters in the right order

Re: How to Extract Height in meter using DSM?

AkhilChhibber1 — Fri, 16 Feb 2018 08:19:55 GMT

Sir, I got what your are saying and I really really appreciate your help.

What I am not getting is not regarding how to subtract 2 raster. The thing what I wanted to know is how to get the elevation data i.e. height of particular area that too particularly in meter.

I mean weather we need a DSM for it or a DTM or both or what?????

Re: How to Extract Height in meter using DSM?

AkhilChhibber1 — Fri, 16 Feb 2018 09:00:12 GMT

Above is the attribute table of points which I generated as a result of the tool "Add Surface Information".

The raster I used in the tool "Add Surface Information" was the raster being generated as a result of output of raster calculator i.e. DSM - DTM.

Now what is this Z value. Is this the height of building. If Yes what is the unit of this. I am really very very confused as this is the first time I am doing this. By the way thanks a lot in advance.

Re: How to Extract Height in meter using DSM?

JayantaPoddar — Fri, 16 Feb 2018 09:55:49 GMT

The values of Building heights look too low to be true (Some have negative values as well).

Are you sure one of the rasters is actually a DTM?

What is the cell-size of the DSM, DTM and the Difference rasters?

Also could you provide the Min-Max values of DSM and DTM rasters?

It looks like you have sorted the records in ascending order of the Z-value. What values do you see when you sort it in descending order?

Re: How to Extract Height in meter using DSM?

AkhilChhibber1 — Fri, 16 Feb 2018 10:21:51 GMT

BELOW IS THE LIST OF ANSWERS TO YOUR QUESTIONS:

Question 1: Are you sure one of the rasters is actually a DTM?

Answer 1: Yes sir, I have generated DSM and DTM both as a result of drone2map i.e. by processing of drone images.

Question 2: What is the cell-size of the DSM, DTM and the Difference rasters?

Answer 2: Attached below is the image which shows cell size of DSM as (0.02421, 0.02421), DTM as (0.12104, 0.12104) and the difference raster as (0.12104, 0.12104).

Question 3: Also could you provide the Min-Max values of DSM and DTM raster?

Answer 3 : DSM (Min. = -10.7023 and Max = 64.5238)

DTM (Min. = -10.6558 and Max = 48.2257)

The minimum and maximum values can also be confirmed as per the screenshot below:

Question 4: It looks like you have sorted the records in ascending order of the Z-value. What values do you see when you sort it in descending order?

Answer 4: Attached below is the image which shows values sorted in descending order of Z value.

Re: How to Extract Height in meter using DSM?

DanPatterson_Retired — Fri, 16 Feb 2018 11:07:55 GMT

So basically you are saying you don't have rasters at all, but points.

Make rasters from the points, then subtract them... but you have differences in the cell size, so be aware

This is really a drone2map place question

Re: How to Extract Height in meter using DSM?

XanderBakker — Fri, 16 Feb 2018 12:16:12 GMT

Do you only have building points or do you have access to building footprints as polygons?. What I see from you screen shot of you DTM is that it includes higher values where the buildings have been filtered out.

You have to keep in mind that with Drone2Map the DSM is based on "measurements" and the DTM is a derivative (hence the lower resolution with a factor 5). Most likely you would like to use the elevation at the streets as the DTM value, but currently inside the buildings values increment (lighter areas).

In case you have access to building footprints you could:

convert them to raster (using the ID)
use expand to make the areas a bit larger
use zonal statistics to define the minimum height inside each expanded footprint
combine that result to replace the DTM values
obtain the object height by calculating DSM - corrected DTM

Re: How to Extract Height in meter using DSM?

rahulverma — Sat, 17 Feb 2018 06:57:00 GMT

Sir, Actually may be I am using the wrong terminology because of which I am not trying to write in words what exactly I want.

Basically i am doing digitizing and I somehow want height data. I have DSM so my question was can I extract height of a building using DSM data??????????

Re: How to Extract Height in meter using DSM?

rahulverma — Sat, 17 Feb 2018 06:59:37 GMT

Yes sir you are correct. I have access to building foot print which I have drafted myself. What I want is to add a field in my building shapefile of name height and get height of each building shapefile. How should I do that sir(as I am not aware regarding how to convert shapefile to raster)????????????