Opened 12 years ago

Last modified 9 years ago

#1781 new defect

v.to.db: slope: slope steepness of vector line or boundary - what

Reported by: hellik Owned by: grass-dev@…
Priority: major Milestone: 6.4.6
Component: Vector Version: svn-releasebranch64
Keywords: v.to.db, slope Cc:
CPU: x86-64 Platform: MSWindows 7

Description

hi,

following example with the nc sample dataset: 

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

for slope following values are calculated: 

v.report map=mystreams3d@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)

Attachments (1)

vtodbslope.png​ (57.8 KB ) - added by hellik 12 years ago.

Download all attachments as: .zip

Change History (3)

by hellik, 12 years ago

Attachment: vtodbslope.png​ added

in reply to:  description comment:1 by hellik, 12 years ago

Priority: normal → major
Type: enhancement → defect

Replying to hellik:

there positive and negative values.

see also attached screenshots, it depends if the line direction is up-/down-slope.

example from the screenshot 

cat					1				2
line direction		down slope		up slope
slope				-0,512637		0,527028
startx				4537928,996710	4536897,402568
starty				2643173,941177	2643324,787491
startz				1783,171319		1174,266273
endx				4536887,670548	4537919,264690
endy				2643144,745117	2643344,251531
endz				1161,194798		1808,083109

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

any ideas for this questions?

comment:2 by neteler, 9 years ago

Milestone: 6.4.3 → 6.4.6
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