Re: [GRASS-user] get the shifted minimum from a raster series

[Frank David]

Hi Micha,


Thank you for your email. Your script is very interesting, but I think I 
cannot use it because:


1- you make a sum of your viewshed list, and each viewshed value is 0 or 
1 (hidden or visible). But my problem is with viewshed values from 0 
upto 250 (for each viewshed this is the hidden height from a viewpoint). 
So make a sum has no sens.


2- you search the pourcent of visible terrain from all viewpoints, and I 
want find pourcent of viewpoints able to see terrain (actually to not 
see the maximum hidden height above terrain)


Tell me if I'm wrong...


I wrote a script with garray.array() which read the value for each 
specific x,y cell coordinates from all viewshed rasters, create a list 
of data, sort that list, and get the shifted min (according to my 
tolerance, for example 80% of 100 viewpoints get the twentieth smallest 
value). In that way Each cell of my output raster give the hidden height 
from 80% of my viewpoints. The script is working, but I believe that 
adding this function in r.series could be useful.



Cheers,

Frank


Le 15/02/2019 à 15:52, Micha Silver a écrit :


Hello Frank:


On 2/7/19 3:16 PM, Frank David wrote:


I forgot one thing to well understand my wish. Each viewshed raster 
is a r.series (250-sum) of 250 r.viewshed with 2m target and 0 upto 
250m terrain height. So each raster gives the hidden height of a 
building (250m max) anywhere on the region from a specific point of 
view. The purpose is to get the area of hidden wind turbine from 
roads for a specific wind turbine height.


Cheers,

Frank



A friend and I were working on an idea some months ago that might be 
of interest. Not the same as your project but the method I used is 
similar.



The search and rescue teams here are interested to see what areas were 
actually visible after they finish searching along a certain route, 
and what areas were not seen at all. I used the same approach as you, 
creating a series of overlapping r.viewshed intermediate rasters.



After seeing your post, I have added new input parameters for minimum 
and maximum values of overlap. The user can enter percents of minimum 
or maximum viewshed overlaps. Suppose I put in 20 as the minimum, then 
only those pixels with at least 20% of the total number of viewsheds 
will be shown. Similarly, if I enter 80 as the maximum, then only 
those pixels with less than 80% of the maximum number of viewsheds 
will appear in the final raster.



If you are on Gitlab, you can clone the files: No documentation yet :-(

https://gitlab.com/tsvibar/route_viewshed


If you do adopt any of this script, I'd appreciate to hear of any bugs 
or suggestions for improvement. If the script raises any interest, 
I'll add it to the Addons.



Regards,

Micha



Le 07/02/2019 à 12:48, Frank David a écrit :


Hi,

Thanks for your reply. I can have numerous raster (several 
hundreds). I want to find a minimum but with a tolerance, it's why I 
want to be able to shift the value. In fact I want to sort the value 
of my all input raster for each x,y cell and get the second or 
third, or any position in the sorted list, to build my output 
raster. My application is to get the area not visible from a road (I 
did 1600 viewshed raster from the roads every 250m). I want a 
tolerance in order that one point of view (top of hill) does not 
reduce too much the hidden area. To do so, a fixed number of my 
point of view (20%) does not reduce the hidden area. The result is 
the area is hidden from 80% of the road.


I already wrote a python script that read all rasters for each x,y 
cell and make a array(), sort the array values, and build a raster. 
It works on reasonable number of cell, but seems to fails with large 
number of cells. I'm not a programmer !


I wondered if this kind of treatment exists already in Grass.

If somebody wants to hemps me to develop this, I could be nice. But 
I think it could be an improvement of r.series function.


Sorry for my bad english, I hope you have understand my wishes !

Cheers

Frank

Le 07/02/2019 à 12:04, Veronica Andreo a écrit :

Hi Ken,

There isn't any build-in function for that in grass, afaik. 
Depending on how long is your series, you could shift the map list 
you use in each run and then use r.univar on each output from 
r.series to get the minimum and by comparison, get the second 
minimum of the series of maps (a scalar).


However, if what you need is a map of second minimums per pixel, I 
believe that might require some programming for a new function... 
Do you know any other software which has this function? Maybe, if 
there's such thing in Python for example, it could be recycled or 
used with grass maps in a script... Dunno, just thinking out loud


best,
Vero

El jue., 7 feb. 2019 07:16, Ken Mankoff > escribió:


Hi Frank,

On 2019-02-07 at 08:27 +0100, Frank David
mailto:frank.da...@geophom.fr>>
wrote...
> I try to find how to get the shifted minimum value of 

Re: [GRASS-user] get the shifted minimum from a raster series

[Micha Silver]

  
  

On 2/16/19 12:00 PM, Frank David wrote:


  
  Hi Micha,
  
  
  Thank you for your email. Your script is very interesting, but
I think I cannot use it because:
  1- you make a sum of your viewshed list, and each viewshed
value is 0 or 1 (hidden or visible). But my problem is with
viewshed values from 0 upto 250 (for each viewshed this is the
hidden height from a viewpoint). So make a sum has no sens.
  
  2- you search the pourcent of visible terrain from all
viewpoints, and I want find pourcent of viewpoints able to see
terrain (actually to not see the maximum hidden height above
terrain)
  Tell me if I'm wrong...
  



You're right. That is my understanding also.

What I was thinking was to use the "max_overlap" parameter to
  find all areas in the search radius that are visible by at most
  i.e. 80% of the viewsheds. Then invert that raster - wherever
  there is some value, set to NULL, and wherever the value is NULL
  set to the DTM elevation (+ turbine height). That will give you
  the height at all pixels that are not visible from 20% of the
  viewsheds. 


In any case it's an interesting application. 




   
  I wrote a script with garray.array() which read the value for
each specific x,y cell coordinates from all viewshed rasters,
create a list of data, sort that list, and get the shifted min
(according to my tolerance, for example 80% of 100 viewpoints
get the twentieth smallest value). In that way Each cell of my
output raster give the hidden height from 80% of my viewpoints.
The script is working, but I believe that adding this function
in r.series could be useful.
  
  
  Cheers,
  Frank
  
  
  Le 15/02/2019 à 15:52, Micha Silver a
écrit :
  
  


Hello Frank:


On 2/7/19 3:16 PM, Frank David
  wrote:


  
  I forgot one thing to well understand my wish. Each
viewshed raster is a r.series (250-sum) of 250 r.viewshed
with 2m target and 0 upto 250m terrain height. So each
raster gives the hidden height of a building (250m max)
anywhere on the region from a specific point of view. The
purpose is to get the area of hidden wind turbine from roads
for a specific wind turbine height.
  Cheers,
  Frank



A friend and I were working on an idea some months ago that
  might be of interest. Not the same as your project but the
  method I used is similar.


The search and rescue teams here are interested to see what
  areas were actually visible after they finish searching along
  a certain route, and what areas were not seen at all. I used
  the same approach as you, creating a series of overlapping
  r.viewshed intermediate rasters. 


After seeing your post, I have added new input parameters for
  minimum and maximum values of overlap. The user can enter
  percents of minimum or maximum viewshed overlaps. Suppose I
  put in 20 as the minimum, then only those pixels with at least
  20% of the total number of viewsheds will be shown. Similarly,
  if I enter 80 as the maximum, then only those pixels with less
  than 80% of the maximum number of viewsheds will appear in the
  final raster. 



If you are on Gitlab, you can clone the files: No
  documentation yet :-(
https://gitlab.com/tsvibar/route_viewshed


If you do adopt any of this script, I'd appreciate to hear of
  any bugs or suggestions for improvement. If the script raises
  any interest, I'll add it to the Addons.


Regards,
Micha




   
  Le 07/02/2019 à 12:48, Frank
David a écrit :
  
  

Hi,
Thanks for your reply. I can have numerous raster
  (several hundreds). I want to find a minimum but with a
  tolerance, it's why I want to be able to shift the value.
  In fact I want to sort the value of my all input raster
  for each x,y cell and get the second or third, or any
  position in the sorted list, to build my output raster. My
  application is to get the area not visible from a road (I
  did 1600 viewshed raster from the roads every 250m). I
  want a tolerance in order that one point of view (top of
  hill) does not reduce too much the hidden area. To 

Re: [GRASS-user] get the shifted minimum from a raster series

[Micha Silver]

  
  
Hello Frank:


On 2/7/19 3:16 PM, Frank David wrote:


  
  I forgot one thing to well understand my wish. Each viewshed
raster is a r.series (250-sum) of 250 r.viewshed with 2m target
and 0 upto 250m terrain height. So each raster gives the hidden
height of a building (250m max) anywhere on the region from a
specific point of view. The purpose is to get the area of hidden
wind turbine from roads for a specific wind turbine height.
  Cheers,
  Frank



A friend and I were working on an idea some months ago that might
  be of interest. Not the same as your project but the method I used
  is similar.


The search and rescue teams here are interested to see what areas
  were actually visible after they finish searching along a certain
  route, and what areas were not seen at all. I used the same
  approach as you, creating a series of overlapping r.viewshed
  intermediate rasters. 


After seeing your post, I have added new input parameters for
  minimum and maximum values of overlap. The user can enter percents
  of minimum or maximum viewshed overlaps. Suppose I put in 20 as
  the minimum, then only those pixels with at least 20% of the total
  number of viewsheds will be shown. Similarly, if I enter 80 as the
  maximum, then only those pixels with less than 80% of the maximum
  number of viewsheds will appear in the final raster. 



If you are on Gitlab, you can clone the files: No documentation
  yet :-(
https://gitlab.com/tsvibar/route_viewshed


If you do adopt any of this script, I'd appreciate to hear of any
  bugs or suggestions for improvement. If the script raises any
  interest, I'll add it to the Addons.


Regards,
Micha




   
  Le 07/02/2019 à 12:48, Frank David a
écrit :
  
  

Hi,
Thanks for your reply. I can have numerous raster (several
  hundreds). I want to find a minimum but with a tolerance, it's
  why I want to be able to shift the value. In fact I want to
  sort the value of my all input raster for each x,y cell and
  get the second or third, or any position in the sorted list,
  to build my output raster. My application is to get the area
  not visible from a road (I did 1600 viewshed raster from the
  roads every 250m). I want a tolerance in order that one point
  of view (top of hill) does not reduce too much the hidden
  area. To do so, a fixed number of my point of view (20%) does
  not reduce the hidden area. The result is the area is hidden
  from 80% of the road.

I already wrote a python script that read all rasters for
  each x,y cell and make a array(), sort the array values, and
  build a raster. It works on reasonable number of cell, but
  seems to fails with large number of cells. I'm not a
  programmer !

I wondered if this kind of treatment exists already in Grass.
  

If somebody wants to hemps me to develop this, I could be
  nice. But I think it could be an improvement of r.series
  function.
Sorry for my bad english, I hope you have understand my
  wishes !

Cheers
Frank

Le 07/02/2019 à 12:04, Veronica
  Andreo a écrit :


  
  Hi Ken,


There isn't any build-in function for that
  in grass, afaik. Depending on how long is your series, you
  could shift the map list you use in each run and then use
  r.univar on each output from r.series to get the minimum
  and by comparison, get the second minimum of the series of
  maps (a scalar). 


However, if what you need is a map of second
  minimums per pixel, I believe that might require some
  programming for a new function... Do you know any other
  software which has this function? Maybe, if there's such
  thing in Python for example, it could be recycled or used
  with grass maps in a script... Dunno, just thinking out
  loud


best,
Vero
  
  
  
El jue., 7 feb. 2019 07:16, Ken Mankoff 
  escribió:

Hi
  Frank,
  
  On 2019-02-07 at 08:27 +0100, Frank David 
  wrote...
  > I try to find how to get the shifted minimum value of
  a series of
  > raster map. I want to shift by one, or more, the
   

Re: [GRASS-user] get the shifted minimum from a raster series

[Frank David]

I forgot one thing to well understand my wish. Each viewshed raster is a 
r.series (250-sum) of 250 r.viewshed with 2m target and 0 upto 250m 
terrain height. So each raster gives the hidden height of a building 
(250m max) anywhere on the region from a specific point of view. The 
purpose is to get the area of hidden wind turbine from roads for a 
specific wind turbine height.


Cheers,

Frank

Le 07/02/2019 à 12:48, Frank David a écrit :


Hi,

Thanks for your reply. I can have numerous raster (several hundreds). 
I want to find a minimum but with a tolerance, it's why I want to be 
able to shift the value. In fact I want to sort the value of my all 
input raster for each x,y cell and get the second or third, or any 
position in the sorted list, to build my output raster. My application 
is to get the area not visible from a road (I did 1600 viewshed raster 
from the roads every 250m). I want a tolerance in order that one point 
of view (top of hill) does not reduce too much the hidden area. To do 
so, a fixed number of my point of view (20%) does not reduce the 
hidden area. The result is the area is hidden from 80% of the road.


I already wrote a python script that read all rasters for each x,y 
cell and make a array(), sort the array values, and build a raster. It 
works on reasonable number of cell, but seems to fails with large 
number of cells. I'm not a programmer !


I wondered if this kind of treatment exists already in Grass.

If somebody wants to hemps me to develop this, I could be nice. But I 
think it could be an improvement of r.series function.


Sorry for my bad english, I hope you have understand my wishes !

Cheers

Frank

Le 07/02/2019 à 12:04, Veronica Andreo a écrit :

Hi Ken,

There isn't any build-in function for that in grass, afaik. Depending 
on how long is your series, you could shift the map list you use in 
each run and then use r.univar on each output from r.series to get 
the minimum and by comparison, get the second minimum of the series 
of maps (a scalar).


However, if what you need is a map of second minimums per pixel, I 
believe that might require some programming for a new function... Do 
you know any other software which has this function? Maybe, if 
there's such thing in Python for example, it could be recycled or 
used with grass maps in a script... Dunno, just thinking out loud


best,
Vero

El jue., 7 feb. 2019 07:16, Ken Mankoff > escribió:


Hi Frank,

On 2019-02-07 at 08:27 +0100, Frank David mailto:frank.da...@geophom.fr>>
wrote...
> I try to find how to get the shifted minimum value of a series of
> raster map. I want to shift by one, or more, the "minimum"
value found
> on each cell to get the "almost minimum" of the series. Is there an
> available function/method to do that ?

I don't think I fully understand what you want. Are you working
with strds? You mention "series". If I wanted to get the
second-minimum of a single raster, I would use r.stats with the
"-1" flag, sort, and search for the 2nd (or 2nd-to-last).

  -k.

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Re: [GRASS-user] get the shifted minimum from a raster series

[Frank David]

Hi,

Thanks for your reply. I can have numerous raster (several hundreds). I 
want to find a minimum but with a tolerance, it's why I want to be able 
to shift the value. In fact I want to sort the value of my all input 
raster for each x,y cell and get the second or third, or any position in 
the sorted list, to build my output raster. My application is to get the 
area not visible from a road (I did 1600 viewshed raster from the roads 
every 250m). I want a tolerance in order that one point of view (top of 
hill) does not reduce too much the hidden area. To do so, a fixed number 
of my point of view (20%) does not reduce the hidden area. The result is 
the area is hidden from 80% of the road.


I already wrote a python script that read all rasters for each x,y cell 
and make a array(), sort the array values, and build a raster. It works 
on reasonable number of cell, but seems to fails with large number of 
cells. I'm not a programmer !


I wondered if this kind of treatment exists already in Grass.

If somebody wants to hemps me to develop this, I could be nice. But I 
think it could be an improvement of r.series function.


Sorry for my bad english, I hope you have understand my wishes !

Cheers

Frank

Le 07/02/2019 à 12:04, Veronica Andreo a écrit :

Hi Ken,

There isn't any build-in function for that in grass, afaik. Depending 
on how long is your series, you could shift the map list you use in 
each run and then use r.univar on each output from r.series to get the 
minimum and by comparison, get the second minimum of the series of 
maps (a scalar).


However, if what you need is a map of second minimums per pixel, I 
believe that might require some programming for a new function... Do 
you know any other software which has this function? Maybe, if there's 
such thing in Python for example, it could be recycled or used with 
grass maps in a script... Dunno, just thinking out loud


best,
Vero

El jue., 7 feb. 2019 07:16, Ken Mankoff > escribió:


Hi Frank,

On 2019-02-07 at 08:27 +0100, Frank David mailto:frank.da...@geophom.fr>>
wrote...
> I try to find how to get the shifted minimum value of a series of
> raster map. I want to shift by one, or more, the "minimum" value
found
> on each cell to get the "almost minimum" of the series. Is there an
> available function/method to do that ?

I don't think I fully understand what you want. Are you working
with strds? You mention "series". If I wanted to get the
second-minimum of a single raster, I would use r.stats with the
"-1" flag, sort, and search for the 2nd (or 2nd-to-last).

  -k.

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Re: [GRASS-user] get the shifted minimum from a raster series

[Veronica Andreo]

Hi Ken,

There isn't any build-in function for that in grass, afaik. Depending on
how long is your series, you could shift the map list you use in each run
and then use r.univar on each output from r.series to get the minimum and
by comparison, get the second minimum of the series of maps (a scalar).

However, if what you need is a map of second minimums per pixel, I believe
that might require some programming for a new function... Do you know any
other software which has this function? Maybe, if there's such thing in
Python for example, it could be recycled or used with grass maps in a
script... Dunno, just thinking out loud

best,
Vero

El jue., 7 feb. 2019 07:16, Ken Mankoff  escribió:

> Hi Frank,
>
> On 2019-02-07 at 08:27 +0100, Frank David 
> wrote...
> > I try to find how to get the shifted minimum value of a series of
> > raster map. I want to shift by one, or more, the "minimum" value found
> > on each cell to get the "almost minimum" of the series. Is there an
> > available function/method to do that ?
>
> I don't think I fully understand what you want. Are you working with
> strds? You mention "series". If I wanted to get the second-minimum of a
> single raster, I would use r.stats with the "-1" flag, sort, and search for
> the 2nd (or 2nd-to-last).
>
>   -k.
>
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Re: [GRASS-user] get the shifted minimum from a raster series

[Ken Mankoff]

Hi Frank,

On 2019-02-07 at 08:27 +0100, Frank David 
wrote...
> I try to find how to get the shifted minimum value of a series of
> raster map. I want to shift by one, or more, the "minimum" value found
> on each cell to get the "almost minimum" of the series. Is there an
> available function/method to do that ?

I don't think I fully understand what you want. Are you working with strds? You 
mention "series". If I wanted to get the second-minimum of a single raster, I 
would use r.stats with the "-1" flag, sort, and search for the 2nd (or 
2nd-to-last).

  -k.

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