[GRASS-user] Elevation above a river

[Shane Carey]

Would you be able to give me an example of this please?
This software is really really good. I absolutely love it.
Keep up the great work!!

Le gach dea ghui,
*Shane Carey*
*GIS and Data Solutions Consultant*

On Sat, Sep 22, 2018 at 3:25 PM, johannesradinger <
johannesradinger at gmail.com> wrote:

> You could also try larger size parameters depending on the degree of
> filtering you want to achieve
>
>
>
> Sent from my Samsung Galaxy smartphone.
>
> -------- Original message --------
> From: Shane Carey <careyshan at gmail.com>
> Date: 22/09/2018 15:47 (GMT+01:00)
> To: johannesradinger <johannesradinger at gmail.com>
> Cc: Markus Neteler <neteler at osgeo.org>, GRASS user list <
> grass-user at lists.osgeo.org>
> Subject: Re: [GRASS-user] Elevation above a river
>
> No worries, I'm not seeing any differences in the original and the
> filtered cells. I've tried mode and max methods
>
> Thanks
>
> Le gach dea ghui,
> *Shane Carey*
> *GIS and Data Solutions Consultant*
>
> On Sat, Sep 22, 2018 at 2:39 PM, johannesradinger <
> johannesradinger at gmail.com> wrote:
>
>> Sorry I ment method=mode or median as stated by Markus N.
>>
>>
>>
>> Sent from my Samsung Galaxy smartphone.
>>
>> -------- Original message --------
>> From: Shane Carey <careyshan at gmail.com>
>> Date: 22/09/2018 15:05 (GMT+01:00)
>> To: Johannes Radinger <johannesradinger at gmail.com>
>> Cc: Markus Neteler <neteler at osgeo.org>, GRASS user list <
>> grass-user at lists.osgeo.org>
>> Subject: Re: [GRASS-user] Elevation above a river
>>
>> This works a treat - super stuff - thanks Johannes.
>>
>> Could you point me in the direction of an algorithim with Grass that can
>> do the following:
>>
>> # Clean some of the spurious cells etc. (using some kind of neighbourhood
>> filtering)
>>
>> Thanks very much
>>
>> Le gach dea ghui,
>> *Shane Carey*
>> *GIS and Data Solutions Consultant*
>>
>> On Sun, Sep 16, 2018 at 8:46 PM, Johannes Radinger <
>> johannesradinger at gmail.com> wrote:
>>
>>> That is were the third step should follow, i.e. using r.mapcalc to
>>> identify all the cells that are 1m higher than the grown river
>>> (irrespective in which distance from the river these cells are located).
>>> The rasterized area could then be translated into a vector format using
>>> r.to.vect.
>>>
>>> Here a small example of how the working flow could be using the North
>>> Caroline example dataset:
>>> ##############
>>> # Set region
>>> g.region raster=elevation at PERMANENT
>>>
>>> # Extract elevation of the streams
>>> r.mapcalc --o expression="streams_elevation = if(
>>> streams_derived at PERMANENT, elevation at PERMANENT,null())"
>>>
>>> # Grow stream_elevation map by a some hundred meters
>>> r.grow -m --overwrite input=streams_elevation
>>> output=streams_elevation_grow radius=500
>>>
>>> # Calculate difference between original elevatoin and stream channel
>>> elevation
>>> r.mapcalc expression="stream_elevation_diff = elevation at PERMANENT -
>>> streams_elevation_grow" --overwrite
>>>
>>> # Extract areas that are than x meters higher than stream channel
>>> elevation
>>> r.mapcalc expression="stream_elevation_diff_smaller1 = if(
>>> stream_elevation_diff < 1,1,null())" --overwrite
>>>
>>> # Maybe here it needs some cleaning of spurious cells etc. (using some
>>> kind of neighbourhood filtering)
>>>
>>> # Raster areas to a vector area (with smoothed corners; s-flag)
>>> r.to.vect -s --overwrite input=stream_elevation_diff_smaller1
>>> output=stream_elevation_diff_smaller1_area type=area
>>> ##############
>>>
>>> HTH
>>> /Johannes
>>>
>>> On Sun, Sep 16, 2018 at 8:53 PM Shane Carey <careyshan at gmail.com> wrote:
>>>
>>>> Hey Johannes,
>>>>
>>>> Thanks for your reply. How does r.grow work if let's say the height
>>>> above the river reaches 1m at 3meters away from the river. And in an other
>>>> area it reaches the 1meter height at 2meters away from the river. Is it
>>>> able to follow that line?
>>>>
>>>> Thanks
>>>>
>>>> On Domh 16 MFómh 2018 at 17:21, Johannes Radinger <
>>>> johannesradinger at gmail.com> wrote:
>>>>
>>>>> To me this looks like a flooding-related question, i.e. to extract the
>>>>> shore lines of a river if it's water level is raised by 1m or 3m?
>>>>> Maybe (1) extract the raster cells of the elevation map that
>>>>> represents the river channel, (2) then apply r.grow and (3) then r.mapcalc
>>>>> to subtract the grown river channel from the original elevation map.
>>>>> /Johannes
>>>>>
>>>>> On Sun, Sep 16, 2018 at 5:16 PM Markus Neteler <neteler at osgeo.org>
>>>>> wrote:
>>>>>
>>>>>> Hi,
>>>>>>
>>>>>> Shane Carey <careyshan at gmail.com> schrieb am Fr., 14. Sep. 2018,
>>>>>> 23:02:
>>>>>>
>>>>>>> Hi All,
>>>>>>>
>>>>>>> Does anyone know is it possible to calculate the elevation above a
>>>>>>> river channel (actual river network that was digitised as opposed to being
>>>>>>> extracted from a DTM) from a DTM and create a polygon from it.
>>>>>>>
>>>>>>> I need to calculate heights of 1m and 3m above a river channel on
>>>>>>> both sides of the channel and create a polygon from it.
>>>>>>>
>>>>>>
>>>>>> This isn't clear to me. Could you elaborate?
>>>>>>
>>>>>> Best
>>>>>> Markus
>>>>>>
>>>>>>
>>>>>> Thanks all.
>>>>>>>
>>>>>>> Le gach dea ghui,
>>>>>>> *Shane Carey*
>>>>>>> *GIS and Data Solutions Consultant*
>>>>>>> _______________________________________________
>>>>>>> grass-user mailing list
>>>>>>> grass-user at lists.osgeo.org
>>>>>>> https://lists.osgeo.org/mailman/listinfo/grass-user
>>>>>>
>>>>>> _______________________________________________
>>>>>> grass-user mailing list
>>>>>> grass-user at lists.osgeo.org
>>>>>> https://lists.osgeo.org/mailman/listinfo/grass-user
>>>>>
>>>>> --
>>>> Le gach dea ghui,
>>>> *Shane Carey*
>>>> *GIS and Data Solutions Consultant*
>>>>
>>>
>>
>
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