User Forum of Software BASEMENT

Guillaume Bourlard

User

Registered: 2015-07-28

Posts: 3

Interpolation tool: very long calculation

Hello,
I am using Basemesh on Qgis 2.8.
As Basis I have a DTM with one point every meters. I want to generate a quality mesh with a max area of 5 meters. The generation of the Elevetion Mesh and Quality Mesh are quite long (some hours for a model of 0.7 km²) but work with a 64 Bits Computer.
The Problem is that using the elevation Tool, the program is working during days without results. (I stop the process).
With the Tutorial everything works without Problems.

I want to now:
Is it because the DTM resolution (viz. the Elevetion Mesh resolution) is smaller as the Quality Mesh resolution?
Is it because of my Hardware:
Windows 7
Processor Interl(R) Core(TM) i5 CPU 750 @2.67GHz 2.80 GHz
RAM:4.00G
System: 64 Bit

I found a temporary solution: I export the Quality Mesh without Elevation as .2dm and do the interpolation in SMS. But it is not a viable solution for me. ( the goal is not to use SMS for preprocessing!)

Best regards.

Sam

Developer

From: VAW - ETH Zurich

Registered: 2014-09-04

Posts: 46

Website

Re: Interpolation tool: very long calculation

hi,
if cell numbers get big (>100'000) the performance of BASEmesh is low indeed.
your DTM is a raster file, right? so you have 700'000 data points, regularly spaced, that will result in a elevation mesh with roughly 1.5 million triangles ... I am not surprised that is not working properly!
you said that the quality meshing worked fine? now you can get the elevation for your quality-mesh nodes directly from the raster DTM: BASEmesh -> interpolation -> under "Elevation Data" toggle "digital elevation map"
cheers

Guillaume Bourlard

User

Registered: 2015-07-28

Posts: 3

Re: Interpolation tool: very long calculation

Tahnk you for your asnwer.
It means that if I make some change in my DTM (points from other measure, delate of inapropriate points...) and have dann an irregular DTM, there is no other solution as the interpolation with sms. I mean does the digital elevation map work with TIN?

Sam

Developer

From: VAW - ETH Zurich

Registered: 2014-09-04

Posts: 46

Website

Re: Interpolation tool: very long calculation

in BASEmesh you either interpolate the elevation data from a elevation mesh (TIN) or from raster, which is much faster and works fine even with large data sets.
if you want to stay with all your 700'000 data points and want to have a TIN as DEM, as mentioned before, you won't succeed with BASEmesh.
options are:
- given your manually edited point layer, you can rasterize this data (using QGis tools). then do the fast interpolation from this raster.
- apply some filter to delete data points that do not contain relevant elevation information.
- split your quality mesh into sub domains, and interpolate the elevation data separately. this will power up the performance! afterwards you can merge the mesh again (using standard QGIS tools).
I am sry not to provide a nice solution right away with BASEmesh. the implemented interpolation routines are quite rudimentary (and therefore slow). An improvement as needed there!

Guillaume Bourlard

User

Registered: 2015-07-28

Posts: 3

Re: Interpolation tool: very long calculation

Ok,
Thank you.

Last edited by Guillaume Bourlard (2015-07-28 12:29:50)