Steve,
additional processing steps they can. How does adding code to gdal work?
Just from an observer perspective, it seems that once you have your
additions worked out, attach a diff on on trac ticket. The details
for how to do that are: sign up for an osgeo userid,
I already see a flaw-- the function should be more like:
float GDALSlopeHydroAlg (float* afWin, float fDstNoDataValue, void* pData)
{
// Hydrologic Slope is the max
// local slope btw center cell and adjacent cells
const double radiansToDegrees = 180.0 / M_PI;
GDALSlopeAlgData*
Apologies for the flurry, one more change:
float GDALSlopeHydroAlg (float* afWin, float fDstNoDataValue, void* pData)
{
// Hydrologic Slope is the max
// local slope btw center cell and adjacent cells
const double radiansToDegrees = 180.0 / M_PI;
GDALSlopeAlgData* psData =
Stephen,
It'd be great to see local hydrologic slope in gdaldem.
I've seen a similar discrepancy between field slope and most
GIS-derived slopes. The local max hydrologic slope seems to correspond
much better to our perceived slope on the ground. The integrated slope
used in most GIS, however,
I agree both have their place. Sometimes we get a more consistent or more
interesting answer from our analyses than from our field measurements.
As to the approach, I agree with your assessment, I was thinking
backwards-- one caveat-- how best to handle local minima? Insert a null?
I'm afraid I
Here's what I've settled on. Let me know your thoughts. The algorithm now
correctly calculates angle to lowest nearby point. If it's a local minima,
it instead calculates angle to the nearest high point, which will be a
negative number, so if the user wants to nullify these or use them in
float pafLocalMin = afWin[0];
float pafLocalMax = afWin[0];
for ( int k = 1; k 9; k++)
{
if (afWin[k] pafLocalMin)
{
pafLocalMin=afWin[k];
}
if (afWin[k] pafLocalMax)
{
pafLocalMax=afWin[k];
}
}
Hmm. I don't follow? The revision would be this:
float GDALSlopeHydroAlg (float* afWin, float fDstNoDataValue, void* pData)
{
// Hydrologic Slope is the max
// local slope btw center cell and adjacent cells
const double radiansToDegrees = 180.0 / M_PI;
GDALSlopeAlgData*
On 16-12-2011 03:31, Stephen Mather wrote:
Hmm. I don't follow? The revision would be this:
float GDALSlopeHydroAlg (float* afWin, float fDstNoDataValue, void* pData)
{
// Hydrologic Slope is the max
// local slope btw center cell and adjacent cells
const double
Steve, there are more things I do not understand either. What is
'psData-scale'? Is it the grid cell size?
So, if 'pafLocalMin' is on one of the 4 corners the distance is not cell
size (let's call it DX) but instead sqrt(DX*DX + DX*DX).
And what if data is in geogs? Than DX is clearly
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