[Qgis-user] Vector to Raster Conversion, was :[Euclidean Distance grid creation problem]

Tue Jun 4 21:16:25 PDT 2013

...cool, we shall try that one.

Will be grand; THANKS.
Yours kindly
    F.

Falk Huettmann PhD, Associate Professor
-EWHALE lab- Biology and Wildlife Dept., Institute of Arctic Biology
419 IRVING I, University of Alaska Fairbanks AK 99775-7000 USA
Email fhuettmann at alaska.edu  Phone 907 474 7882 Fax 907 474 6716

-----Original Message-----
From: Ing. Juan M. Bernales [mailto:jm_bernales at hotmail.com]
Sent: Tuesday, June 04, 2013 7:19 PM
To: Falk Huettmann
Cc: QGIS
Subject: Re: [Qgis-user] Vector to Raster Conversion, was :[Euclidean
Distance grid creation problem]

The <Point Sampling Tool> is the plugin you are looking for PS. We are now
looking for a >>>>>tool to intersect the grids with points<<<<<<<
(drill-down, to grab the underlying point layer values from grids. Can that
be done in qgis too ? We use extract in R, or intersect in Hawths tools
(GME; works usually best), or>>>>>>> Extract Values to Points<<<<<<<< in
ArcGIS). Thanks indeed for any pointers.

-----Mensaje original-----
From: Falk Huettmann
Sent: Tuesday, June 04, 2013 4:43 PM
To: tech at wildintellect.com
Cc: qgis-user ; jeffrey_evans at tnc.org ; Michael Lindgren ; 云
Subject: Re: [Qgis-user] Vector to Raster Conversion, was :[Euclidean
Distance grid creation problem]

Ah, thanks indeed Alex.

Yes, for the 'grey' map legend, setting the Min to Max values (you find the
max in Histogram tab) and Stretch them out makes it work (lower left
setting).

One ought to know...(I have similar legend display issues with ArcGIS
sometimes)

Wow, thanks; very best
   F.

PS. We are now looking for a tool to intersect the grids with points
(drill-down, to grab the underlying point layer values from grids. Can that
be done in qgis too ? We use extract in R, or intersect in Hawths tools
(GME; works usually best), or Extract Values to Points in ArcGIS). Thanks
indeed for any pointers.

-----Original Message-----
From: Alex Mandel [mailto:tech_dev at wildintellect.com]
Sent: Tuesday, June 04, 2013 1:12 PM
To: Falk Huettmann
Cc: qgis-user
Subject: Re: [Qgis-user] Vector to Raster Conversion, was :[Euclidean
Distance grid creation problem]

I ran your data, it worked fine for me. Yes initially it all looks 1 color.
After going into the Properties. choosing to use Custom Min/Max values,
Selecting to Load from Actual, and stretching min/max. I can see the data no
problem.

I can see why sampling randomly with the info tool won't work, since you
need to click info exactly where a river line occurs.

http://www.pasteall.org/pic/52841

Thanks,
Alex

On 06/04/2013 01:37 PM, Alex Mandel wrote:
> Ok, now we're getting somewhere. There error is specifically with the
> GDAL rasterize tool (has no direct link to a euclidean distance tool).
>
> Can you please post the GDAL command from the bottom box of that tool?
>
> Thanks,
> Alex
>
> On 06/04/2013 01:14 PM, Falk Huettmann wrote:
>> thanks, re. Euclidean Distance problem,
>>
>> we use the following point layer (shapefile attached) and with the
>> GDAL plugin.
>>
>> We click on Raster, Rasterize (but get a grey canvas; all values in
>> the legend show the same. Using line data has the same effect).
>> We cannot proceed from that.
>>
>>  From there we wanted to get a Euclidean Distance and using Raster,
>> Analyse, Distance.
>>
>> We got stuck in this for over 3 weeks now (paper on Open Source GIS)
>> and wonder how to proceed next and for good progress.
>>
>> Thanks so much for any insights.
>>
>> Very best from Alaska
>>     F.
>>
>>
>>
>>
>>
>> On Mon, Jun 3, 2013 at 9:21 PM, Alex Mandel
>> <tech_dev at wildintellect.com>wrote:
>>
>>> On 06/03/2013 10:02 PM, Falk Huettmann wrote:
>>>
>>>> Dear all,
>>>>
>>>> greetings;
>>>> we are still stuck with creating a Euclidean Distance grid in QGIS
>>>> based on point data (shapefile, projected in lat lon and with an ID
>>>> of 1).
>>>>
>>>> I am aware of the steps shown online, but these create us just a
>>>> grey canvas.
>>>> (we tried different pixel and extent settings too)
>>>>
>>>> We are grateful for  any input (if not resolved, we will probably
>>>> move to R then and other options).
>>>>
>>>> Thanks indeed for any input; more later
>>>>        Falk Huettmann
>>>>
>>>>
>>>>
>>> Grey pixels do not mean no data. Did you check the values of random
>>> pixels with the Info tool?
>>>
>>> Normally in the raster properties you have ask QGIS to calculate the
>>> range of values, and stretch min/max in order to actually see what
>>> you expect, or put in a custom color ramp.
>>>
>>> Also what tutorial did you follow and which tool did you use to
>>> calculate the distance grid.
>>>
>>> Thanks,
>>> Alex
>>>
>>>
>>
>
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