In partnership with NextGen Air Transportation System (NGAT)
Center for Geospatial Analytics (CGA) collects, processes and analyses UAS data
for research and education purposes
Data collection and analysis:
Student projects:
Software:
change detection | processes | microtopography |
water flow erosion landscape evolution |
Motivation:
What we need:
new = if(isnull(UAS), lidar, UAS)
Compute weighted average of DEM $A$ and $B$ on their overlap of width $s$ with weights given by the distance to the edge of DEM $A$.
What do we need?
Distance from the edge of DEM $A$ inwards. |
GRASS GIS:
r.grow.distance -n input=A distance=distance
Linear combination of elevation surfaces $z_{A}$ and $z_{B}$ with weights given by distance $d$ and overlap width $s$ : $$ z_{AB} = z_{A} w + z_{B}(1 - w), \quad\quad w = f(s, d) = \begin{cases} \frac{d}{s} & 0 \leq d < s \\ 1 & d > s \end{cases} $$
Raster algebra expression for $s = 10$ m:
if (distance > 10, A,
if (distance == 0, B,
(1 - distance / 10) * B + (distance / 10 * A)
)
)
0 m | 5 m | 10 m | 20 m |
By taking into account spatially variable differences $\Delta z$ between DEMs $A$ and $B$ along the overlap:
sand model | before change | modified landscape |
g.extension r.patch.smooth url=https://github.com/petrasovaa/r.patch.smooth