# Relative relief

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### #1 GIS xtra Posted 09 August 2011 - 07:58 AM

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Is there any tool to find out relative relief using arc gis or qgis ?

I have to calculate the difference in values between maximum and minimum from a attribute table column (arcgis)). can anyone help me?thanx

### #2 dsl Posted 09 August 2011 - 05:17 PM

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Is there any tool to find out relative relief using arc gis or qgis ?

I have to calculate the difference in values between maximum and minimum from a attribute table column (arcgis)). can anyone help me?thanx

Create a new column and then use the field calculator to calculate the difference (max column - min column).

### #3 NicKV Posted 09 August 2011 - 06:39 PM

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Is there any tool to find out relative relief using arc gis or qgis ?

This is no big deal. It can be done in most GISs.

First you need to answer the question, what is the horizontal distance over which we are interested in knowing the relative relief?

Depending on the distance specified, different realative relief values will be obtained. There is no unique answer, nor correct answer.

Topographic elevation variation across a region can be decomposed to and thus can be considered to be the sum of a number of number of waveforms. At its simplest, the sum of a longwave pattern and a shortwave pattern.

To estimate relative relief you need to subtract the spatially smoothed topography (longwave pattern) from the actual topography, i.e., subtract a spatially smoother version of the DEM from the unsmoothed.

The result is the residual and in the context of a DEM and topography, each array element elevation value within the residual array, is the relative relief within the specified distance of the corresponding array element

The smoothed version of the data can be obtained a number of different ways. These include:

• By performing polynomial regression
• By geostatistical estimation
• By performing a smoothing operation using a suitable convolution filter
• By use of the (fast) fourier transform

Edited by NicKV, 09 August 2011 - 06:41 PM.

### #4 GIS xtra Posted 10 August 2011 - 04:07 AM

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thanks dsl i will try this !!

### #5 GIS xtra Posted 10 August 2011 - 04:15 AM

GIS xtra

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Is there any tool to find out relative relief using arc gis or qgis ?

This is no big deal. It can be done in most GISs.

First you need to answer the question, what is the horizontal distance over which we are interested in knowing the relative relief?

Depending on the distance specified, different realative relief values will be obtained. There is no unique answer, nor correct answer.

Topographic elevation variation across a region can be decomposed to and thus can be considered to be the sum of a number of number of waveforms. At its simplest, the sum of a longwave pattern and a shortwave pattern.

To estimate relative relief you need to subtract the spatially smoothed topography (longwave pattern) from the actual topography, i.e., subtract a spatially smoother version of the DEM from the unsmoothed.

The result is the residual and in the context of a DEM and topography, each array element elevation value within the residual array, is the relative relief within the specified distance of the corresponding array element

The smoothed version of the data can be obtained a number of different ways. These include:

• By performing polynomial regression
• By geostatistical estimation
• By performing a smoothing operation using a suitable convolution filter
• By use of the (fast) fourier transform

Thanks for your response. my interest in on 2o m horizontal distance.

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