1 Dec 2011

Line Slope Calculation in ArcGis 9.3 (using XTools)

You have a polyline, say a path, river, etc., and want to know average slope of each single line.

Use z-values of nodes of polyline and calculate percentual slope by
(line-segment shape_length / z-Difference) * 100

A polyline (PL), a digital elevation model (DEM)

(1) Make point-shp-file from polyline nodes:
Xtools / Feature Conversions / Convert Feature to Points ->
check endpoints "from" & "to" (.. the nodes)
output = "PL_NODES"

(2) z-values at endpt_from & endpt_to:
Spatial Analyst / Extraction / Extract Values to Points ->
Input points = PL_NODES
Raster to extract = DEM
Output = PL_NODES_extr_DEM (...RASTERVALU = z-value)

(3) Get Difference in z-values for a segement (z at endpoint_from, z at endpoint_to):
Summary Statistics ->
Input Table = PL_NODE_extr_DHM,
Statistica Fields = RASTERVALU, Statistic Type = RANGE,
Case Field = Identifier for PL-Segments
output dbf = PL_NODE_dZ

(4) join PL_NODE_dZ to PL:
..use appropriate PL-IDs for joining

(5) add new field [slope_100] to PL:
..then use Field Calculator ->
slope_100 = 100* ( [PL_NODES_dZ.RANGE_RAST] / PL.SHAPE_LEN] )

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