 |
| Titel |
A new approach to reduce the mapping error of landslide inventory maps |
| VerfasserIn |
Michele Santangelo, Ivan Marchesini, Francesco Bucci, Mauro Cardinali, Mauro Rossi, Faith Taylor, Bruce Malamud, Fausto Guzzetti |
| Konferenz |
EGU General Assembly 2013
|
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 15 (2013) |
| Datensatznummer |
250078415
|
|
|
|
|
|
| Zusammenfassung |
| Landslide inventory maps are key in documenting the type and extent of mass movements in
local to regional areas, for both geomorphological studies and landslide hazard assessment.
Geomorphologists usually prepare landslide inventories by aerial photo interpretation
(API) of stereoscopic images aided by field surveys. Criteria adopted for visual
image analyses are derived from the heuristic interpretation of photographic and
morphological features of the image, such as shape, size, color tone, texture and pattern. The
established (traditional) procedure for transferring photo-interpreted information to a GIS
environment involves the manual drawing of information from the aerial photograph to
the topographic base map. In this stage, mapping (i.e., positioning, shape, size)
errors can occur due to (i) the change in scale, from the aerial photographs to the
topographic map, (ii) object deformation in the stereoscopic model, due to the vertical
exaggeration and the conical projection of the aerial photographs, (iii) differences
in topography in the different cartographic media (aerial photographs and base
maps). We recently developed a method to reduce mapping errors which exploits
the ortho-rectification of the aerial photograph and the photo-interpreted thematic
layers, thus avoiding manual transferring of information to the topographic map. The
technique was evaluated in a test area of about 50 km2 in the neighboring of Taormina
(Sicily, Southern Italy), where the information concerning mass movement was
transferred to two inventory maps using the traditional and ortho-rectification technique.
More than 500 landslides pairs have been compared in this test region, ranging in
landlside area between 102 and 107 m2. The mapping error associated with the mapped
features has been evaluated by calculating the mismatch index for each landslide
pair as: E = (A U B)-(A -© B)/(A U B), where A is a landslide of the inventory
obtained using the manual drawing approach and B is a landslide reported using the
ortho-rectification technique, U denotes landslide polygon union, and -© denotes
landslide polygon intersection. The ortho-rectification procedure accounts for a
Root Mean Square Error at defined GCPs lower than 5m. Preliminary results show
that (i) the positional mismatch decreases as landslide area increases, (ii) landslide
areas are generally overestimated when using the traditional method (iii) although
minor differences are observed in the landslide frequency-area statistics between
methods, there is relatively good agreement in the fit of the power law tail of both
distributions. We propose that previous inventories produced using the traditional method
remains correct, but some estimation of positional and size uncertainty should be
included in future work. We outline procedures for estimating this uncertainty. |
|
|
|
|
|
|