difference plot including total volume

[francescarusso]

Hi all,

does anyone know if I would be able to accurately calculate a difference plot (including total volumes) in ArcGIS if I were to request the DTM of the in-survey and the DTM of the out-survey of a dredging volume calculation?

I have ArcGIS 10.2.2 with ONLY Spatial Analyst extension.

If it is possible, any suggestion how to d it?

Many thanks,

F.

[DanPatterson_Retired]

differences are easy to determine in SA, what specifically are you referring to since there is no difference plot tool

EDIT

You wouldn't be referring to the Minus Tool to produce a map of the differences before and after would you?

Your volume estimates would be as accurate as the difference can be represented and the smaller the cell size the better.  Volume would be the differences in the cell counts * the cell area

[francescarusso]

Hi Dan,

thank you very much for answering.

as far as I know they will provide me two different DTM from different surveys and they would like to know if I would be able to make a different plot and calculate the volume as well (something like a grid model volume computation).

As I have no clue where to start (I do not even know if it is something I can do with SA) I am asking for some suggestions.

Thanks

F

[DanPatterson_Retired]

>>> surface
array([[1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 1, 1, 1],
       [1, 1, 1, 1, 1, 1, 1, 1, 1]])
>>> hole
array([[ 1,  1,  1,  1,  1,  1,  1,  1,  1],
       [ 1,  1,  1,  1,  1,  1,  1,  1,  1],
       [ 1,  1,  1,  1,  1,  1,  1,  1,  1],
       [ 1,  1,  1, -1, -2, -3,  1,  1,  1],
       [ 1,  1,  1, -1, -2, -3,  1,  1,  1],
       [ 1,  1,  1, -1, -2, -3,  1,  1,  1],
       [ 1,  1,  1,  1,  1,  1,  1,  1,  1],
       [ 1,  1,  1,  1,  1,  1,  1,  1,  1],
       [ 1,  1,  1,  1,  1,  1,  1,  1,  1]])
>>> 
>>> surface-hole
array([[0, 0, 0, 0, 0, 0, 0, 0, 0],
       [0, 0, 0, 0, 0, 0, 0, 0, 0],
       [0, 0, 0, 0, 0, 0, 0, 0, 0],
       [0, 0, 0, 2, 3, 4, 0, 0, 0],
       [0, 0, 0, 2, 3, 4, 0, 0, 0],
       [0, 0, 0, 2, 3, 4, 0, 0, 0],
       [0, 0, 0, 0, 0, 0, 0, 0, 0],
       [0, 0, 0, 0, 0, 0, 0, 0, 0],
       [0, 0, 0, 0, 0, 0, 0, 0, 0]])
>>> np.sum(surface-hole)
27‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍‍

If we assume each 'cell' is 1m^2 and the values represent depth removed, then the volume is 27 m^3

PS just assume that Surface and Hole are two rasters representing the surface before and after excavation (just used numpy to save making grids)

[francescarusso]

Hi Dan,

thank you very much, but I have really basic knowledge of GIS and I didn't really understand. As far as I understood you said to use Phyton which I have no clue at all as well. Is there any change to do the task in an easier way for me?

Is it not possible to use raster Calculator? Is it wrong?

Sorry about that but I am struggling a lot with this task.

Cheers,

F

[DanPatterson_Retired]

I wasn't suggesting to use python... I was demonstrating what you can do with the spatial analyst... subtract two rasters to get the difference, multiply by the cell area and voila... volume... I just thought an pictoral-ish representation would help without having to go to the problem of creating two grids whose numbers you couldn't see anyway... so again.. the product of area and depth differentials equals volume... simple enough with the spatial analyst without any special tools

[francescarusso]

Hi Dan,

sorry about that. By the way it is more clear now and I found it really helpful.

Thank you very much for your prompt help.

Cheers,

F

[AbdullahAnter]

If you want to calculate dredging volume between 2 raster, use Cut Fill tool.

Cut Fill—Help | ArcGIS Desktop

run this tool . then open attribute table of result raster.

and sum the minus volumes and positive volumes.  

[francescarusso]

Hi Abdullah,

very helpful thanks a lot.

Cheers,

F