Science topics: Geographic Information SystemDigital Terrain Analysis

Science topic

# Digital Terrain Analysis - Science topic

Explore the latest questions and answers in Digital Terrain Analysis, and find Digital Terrain Analysis experts.

Questions related to Digital Terrain Analysis

There are many accuracy measures for validating DEM such as RMSE, mean absolute error, standard deviation etc... But how can I measure the terrain gradients, is it the difference between highest and lowest point of the DEM with respect to a reference DEM? How can I measure spatial distribution of difference DEM?

I am aware of computational costs while working with high resolution data, so this question is more of hypotetical nature and is related to the relevance of friction parameter in inundation modeling. The question is also software(model)-dependent.

It seems impossible since most of analyses are based on 3x3 cell neighborhood but I would like to hear your experiences. I know that some hydrodinamical models like TELEMAC are able to perform this.

Cheers

Looking for information about two sets of questions: (1) What drivers are likely to shape future hydrographic requirements? (2) How are these drivers changing hydrographic requirements? I am interested in a comprehensive overview of trends if, i.e. technical considerations (e.g., big data, bandwidth and connectivity) are as important as future patterns in using the maritime domain (e.g., underwater exploration).

HI, all

I want to get the program to extract Digital terrain models (DTM’s) or

Digital height models (DHM’s) for a certain area from Global Gravity Field Models related to Topography For example dV_ELL_RET2012

In general, the term 'geological complexity' is used qualitatively. Are there any indicators, which can quantify the complexity? Or how the complexity of terrains be compared?

Extracting the morphologic attributes (such as max slope or vertical relief) of a feature at the seabed, or onshore, is only meaningful if the digital terrain model (DTM) used have enough resolution for it. Therefore, what I am looking for is not the smallest feature that can be identified, but the smallest feature that can be characterized with a given resolution.

Consider a pockmark of 40 meters diameter, it can be seen in a dataset with a raster resolution of 10 meters. But, the mean slope value extracted at that resolution will be necessarily lower that if extracted using a 2 m resolution dataset. However, if characterizing a seamount of more than 400 m long the 10 meters resolution should provide accurate values.

Does anyone know of some kind of table defining that is the minimum feature size that can be accurately characterized for different resolutions?

I am introduced with methods for determining the right cell size according to sample characteristics and with visual validation of DEM resolution suitability, but is there any statistical indicator which is calculated after DEM generation (e.g. descriptive statistics), which is relevant ?

Suppose I need to plan the shortest road between two cities located on a hilly terrain. Maximum slope of the road is permitted up to 1 : 10. How to plan the road? Is there any known computer application, which can help on this?

Regards,

Rishi

Basically I have DEM terrain and can load it using several software. The problem is to get the texture/satellite image of the corresponding DEM file to incorporate with the terrain. (I have been using USGS (http://nationalmap.gov/) DEM files))

Thanks in advance.

i want pune cities dem data from 1960 to 2015 for the research purpose....

Halo Members,

I am working with with RapidEye and TSX images therefore need for one coordinate system. My SNAP processing chain has the steps:"Read - SAR-Simulation - GCP-Selection - SARSim-Terrain-Correction - LinearTodB - Write" I am however facing some challenges.

1. Upon using the predefined CRS (EPSG:4326-WGS 84), I get the "/ by zero" error. I do not get this error when using SNAP's default coordinate system. I have tried unchecking the zero values tab on the image properties of the loaded images, but this does not seem to work

2. When trying to write the output file, I get the error "SARSim-Terrain-Correction: please select output band for terrain corrected image". On going back to the SARSim-Terrain-Correction tab, the "Apply radiometric normalization" tab is inactive

I would appreciate your contributions towards this step.

Kuria

Hi everybody,

I need to calculate the wetness index with ArcGis. I know there are a lot of different way to estimate it. I have filled and projected my digital terrain model to obtain (with the hydrology tool) the flow accumulation map. Then I have used the wetness index formula:

ln("FLOW ACC"*900/Tan"slope_in_radians").

Unfortunately I still have negative values.

Can someone help me?

Thanks

What kinds of lineaments detectable in SRTM MDE?

Hobbs (1904), O`leary et al. (1976) and Strieder and Amaro (1997), identified some kinds. What is the acceptance of these types ? Do others exitst?

I have downloaded the Bhuvan DEM of Mumbai, the elevation values are in negative even on the hilly areas.

1.Is this negative values means the whole area is in depression?

2.I want to create a text file with XYZ values of the DEM.

Request to suggest the possible solutions.

How can I download SRTM data of 30 m resolution for research in remote sensing?

I fail to differentiate where I can group the informal settlements, in customary or it should stay independent?. Because I find it in Urban and mostly in peri-urban area. I don't understand in creating a tree diagram for this.

I have been used several methods with SAGA GIS to explore possible clean-up ASTER GDEM V2 (30m) from anomalies and artefacts. But it is very difficult . Any suggestions about programs (saga gis or arcgis) and strategies are welcome.

I am doing erosion modelling, two of the parameters needed would be C factor Map ( I'll be using MODIS time series which is 250 x 250 m) . DEM is 5 meters. How will I deal with this? Any idea/methods on how can I extract C-factor from NDVI.? Thanks in advance.

Terrain analysis through SAGA GIS opensource software.

From the histograms of the the three DEMs, in SRTM-X there are distinct repetitive peaks. Do you have an explanation for these peaks?

Attached figure shows histograms for four different DEMs ( Photogrammetric DEM, ASTER GDEM, SRTM X DEM)

My statement:

Generally, the specification of accuracy measures is based on the assumption that the errors follow a Gaussian distribution without any outlier. But most of the times, this is not the case as objects above the terrain, such as vegetation, buildings, etc. is present which gets ignored during the filtering program.

Peers comment on my statement:

Elevation errors MUST be distributed normally, otherwise many (probably all) the methods to determining the accuracy of the measurements are wrong.

I am researching DEM applications, and in particular algorithms to estimate partial derivatives of height(x,y) given just sparse sample values. To test it, I will need to have analytical expressions of reasonable functions f(x,y) previously used by other researchers in published papers and/or books for DEM applications. Could anyone suggest examples, and the associated reference?