[GRASS-dev] [GRASS GIS] #1781: v.to.db: slope: slope steepness of vector line or boundary - what

[GRASS GIS]

#1781: v.to.db: slope: slope steepness of vector line or boundary - what
----------------------------+-----------------------------------------------
 Reporter:  hellik          |       Owner:  grass-dev@…              
     Type:  enhancement     |      Status:  new                      
 Priority:  normal          |   Milestone:  6.4.3                    
Component:  Vector          |     Version:  svn-releasebranch64      
 Keywords:  v.to.db, slope  |    Platform:  MSWindows 7              
      Cpu:  x86-64          |  
----------------------------+-----------------------------------------------
 hi,

 following example with the nc sample dataset:

 {{{
 g.region -p -a rast=elevation at PERMANENT align=elevation at PERMANENT
 g.copy vect=streams at PERMANENT,mystreams
 v.drape input=mystreams at testvtodb rast=elevation at PERMANENT
 output=mystreams3d method=bilinear
 v.to.db map=mystreams3d at testvtodb option=slope columns=lslope
 }}}

 for slope following values are calculated:

 {{{
 v.report map=mystreams3d at testvtodb option=length units=kilometers
 Displaying column types/names for database connection of layer 1:
 cat|LENGTH|lslope|length
 40102|328.8149|-0.013595|0.10024452212851
 40103|28.42104|-0.036822|0.00866862911730363
 40104|44.41667|-0.047728|0.0135536727783459
 40105|139.24667|-0.039654|0.0424802252327031
 40106|116.87285|-0.001052|0.0356241602630405
 40107|458.31208|-0.007547|0.139722390368716
 40108|721.65613|-0.003072|0.219995119213486
 40109|60.17419|0.022031|0.0183455811863201
 40110|362.36553|-0.03519|0.11052434844217
 40111|473.56751|-0.020228|0.144401746951948
 40112|317.49701|0.000847|0.0968040978132339
 40113|940.93913|-0.011029|0.286884404977333
 40114|533.81131|-0.008499|0.162731935458674
 40115|750.77547|-0.024939|0.228933281109927
 40116|60.2642|-0.07134|0.0184163943699331
 40117|429.15629|-0.05616|0.131052292921112
 40118|253.71239|-0.005919|0.0773330445686153
 40119|25.83167|-0.035896|0.00787858510840826
 40120|188.25525|-0.081927|0.0577275740231798
 40121|236.41829|-0.025056|0.0721007612752627
 40122|24.2134|-0.048417|0.00738892473529617
 40123|808.5051|-0.044623|0.246710220299605
 40124|989.02698|-0.027455|0.301608610707122
 40125|635.93826|-0.036156|0.194051258705588
 40126|468.69024|-0.028593|0.142947452116586
 40127|86.09338|-0.037227|0.0262595682188734
 40128|46.4412|-0.016229|0.0141571715281169
 40129|72.34496|-0.032431|0.0220623924744028
 40130|62.60101|-0.014233|0.0190827578495164
 40131|6.6977|-0.046902|0.00204371077814867
 40132|130.18634|-0.041094|0.0397144228686057
 40133|351.94254|-0.027634|0.107330119519726
 40134|507.74382|-0.02369|0.154820645208978
 40135|43.85154|0.000142|0.0133659751319174
 40136|284.95338|-0.061209|0.0870273800957913
 40137|687.84482|-0.028741|0.209775142412842
 40138|67.44893|-0.02587|0.0205653568467094
 40139|722.70444|-0.028445|0.220472003781462
 40140|229.9372|-0.0598|0.0702297812416715
 40141|168.13355|-0.030217|0.0512849553777092
 40142|796.47932|-0.045388|0.243121741326586
 40143|102.04649|0.034469|0.031184830022709
 40144|90.13488|-0.07636|0.0275536128806874
 40145|482.99786|-0.040011|0.14739330447945
 40146|1157.40373|-0.024864|0.352988115958592
 40147|421.91785|-0.023223|0.128738163181613
 40148|75.48088|-0.040979|0.0230412960814595
 [...]
 }}}

 there positive and negative values.

 '''(1)''' what are the units of this slope value?
 '''(2)''' how to interpret this values?

 maybe some additions to the manual would be fine.

 best regards
 Helmut


 tested with

 {{{
 System Info
 GRASS version: 6.4.3svn
 GRASS SVN Revision: 53658
 GIS Library Revision: 50937 (2012-02-25)
 GDAL/OGR: GDAL 1.9.2, released 2012/10/08
 PROJ4: Rel. 4.8.0, 6 March 2012
 Python: 2.7.2
 wxPython: 2.8.12.1
 Platform: Windows-7-6.1.7601-SP1 (OSGeo4W)
 }}}

-- 
Ticket URL: <http://trac.osgeo.org/grass/ticket/1781>
GRASS GIS <http://grass.osgeo.org>