Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec, Canada :Follow-up(Complement of information)
Hi,
Great find Daniel !
To use directly the GeoTiff images in JOSM, you could try the
ImportImagePlugin, but I haven't tried it.
I put the EO1-ALI images from Earth Observatory online, in WMS and TMS,
with the coordinates included in the GeoTiff files.
Apparently, they were not georeferenced in relation to ground control
points, but with the imagery layer shift option included in Josm, it is
not too difficult to align them to existing data. For example, a shift
of 197; -514 quickly adjusted over Venise-en-Québec seems to give a
reasonable alignment in other areas of the images too.
We could try to improve the georeferencing of the original images with
ground control points, but for now it seems that having a try at mapping
the flood extent with the current setup has higher priority. Let me know
if you think more work on georeferencing would be useful.
URLs:
For the natural color image in TMS (recommended over WMS), use the
following link in Josm:
tms:http://osm.arkemie.org/cgi-bin/tiles/1.0.0/hautrichelieu_coulnat/{zoom}/{x}/{y}.jpg
For the shortwave infrared image in TMS:
tms:http://osm.arkemie.org/cgi-bin/tiles/1.0.0/hautrichelieu_swir/{zoom}/{x}/{y}.jpg
The base WMS URL is :
http://osm.arkemie.org/cgi-bin/osm_wms?map=/mapsite/hautrichelieu.map
Thus, for the natural color image in WMS, use the following link in Josm:
wms:http://osm.arkemie.org/cgi-bin/osm_wms?map=/mapsite/hautrichelieu.mapFORMAT=image/jpegVERSION=1.1.1SERVICE=WMSREQUEST=GetMapLayers=hautrichelieu20110508_natcol;
For the shortwave infrared image in WMS:
wms:http://osm.arkemie.org/cgi-bin/osm_wms?map=/mapsite/hautrichelieu.mapFORMAT=image/jpegVERSION=1.1.1SERVICE=WMSREQUEST=GetMapLayers=hautrichelieu20110508_swir;
Now on to OSM-style-collaborative-iterative flood extent mapping,
without - and probably then with - boots :)
Best wishes,
Jean-Guilhem
Le 28/05/2011 05:53, Daniel Begin a écrit :
Hi all,
I've tried to put my boots on the ground without going there !-).
I found a pretty clear satellite image of the river at its max level
(30-31m) - which doesn't really changed since ...
http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=50577
I made few geometric adjustments to the image and compare the result
with 30m GeoBase and SRTM contours. Geobase contours gives better
results between St-Jean and L'Île aux Noix but from there to the US
boundary, neither GeoBase nor SRTM is right.
I'm trying to produce a flooded area from DEM data while I'm looking
at an image that contains what I'm looking for - the flooded area!
Why not mapping from it? I understand the image can be used -
http://earthobservatory.nasa.gov/ImageUse/
Any idea on how I can use this GeoTiff image in JOSM?
Cheers,
Daniel
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Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec, Canada : Follow-up (Complement of information)
Hi Pierre, The 30 m contour lines from tiles 031h03 and 031h06 (the shapefiles you gave), potentially connected to Richelieu river, have been imported, and put together in relation: http://www.openstreetmap.org/?relation=1602671 Clearly, it is not enough to estimate the flooded zone, for which some kind of flow analysis would be needed, but maybe it can help in some areas, as you wrote. I used ogr2ogr -where ELEVATION=30 ... to extract the 30m contour line, and ogr2osm.py to convert it to .osm, for Josm. Best wishes, Jean-Guilhem Le 27/05/2011 06:30, Brent Fraser a écrit : Pierre, I can't comment on if the 30m contour solution is suitable, but if you want to extract the 30m contours, you could: 1. Use QGIS to extract 30m contour from *_FO.._1.shp files - load shapefile, Open Attribute Table, click on elevation field name to sort table by elevation value. - select all 30m values, click on Layer - Save selection as vector file. Save shapefile 2. Use converter (one of the ones on http://wiki.openstreetmap.org/wiki/Import/Shapefile) to create .osm files (I haven't tried this) 3. Use Josm to load osm files, tag, and update to OSM Best Regards, Brent Fraser On 5/26/2011 8:46 PM, Pierre Béland wrote: Many osm volunteers have worked in the last two days to correct roads, complete Canvec import and add street names. An other task is to estimate the flooded zone along the Richelieu River and Missisquoi Bay in Lake Champlain. One simple approach to determine the flooded zones would be to use the 30 meter contour line from Canvec data. This would be good at least for Richelieu River. These maps from Natural Resources Dept of Canada shows the 30 meter contour line. For the areas I visited last week with volunteers, this line delimits approximately the flooded zone. On monday 23, water level of the Richelieu river went up to approximately 30.8 meters in Saint-Jean-sur-Richelieu. Would it be a good solution to estimate the flooded zone ? If so, any idea, how we can extract 30 meter contour line from shape files using a tool such as Quantum GIS and convert to OSM ? ftp://ftp2.cits.rncan.gc.ca/pub/canvec/50k_shp/031/h/canvec_031h03_shp.zip ftp://ftp2.cits.rncan.gc.ca/pub/canvec/50k_shp/031/h/canvec_031h03_shp.zip ftp://ftp2.cits.rncan.gc.ca/pub/canvec/50k_shp/031/h/canvec_031h06_shp.zip ftp://ftp2.cits.rncan.gc.ca/pub/canvec/50k_shp/031/h/canvec_031h03_shp.zip Below is an example of Toporama map for Saint-Jean-sur-Richelieu, the wms version of Canvec, where we can see the 30 meter contour line. http://atlas.nrcan.gc. ca/auth/english/maps/topo/map?mapsize=525%20466mapxy=1700511.0503883713%20-122536.87132125527scale=2.00feature_na=Saint-Jean-sur-Richelieusearchstring=saint-jean-sur-richelieulayers=fapfeature%20nodata_ntdb_50k%20north_arrow%20other_features%20roads%20hydrography%20boundary%20builtup%20vegetation%20populated_places%20railway%20power_network%20manmade_features%20designated_areas%20water_features%20water_saturated_soils%20relief%20contours%20toponymy%20contourmap_layer[northarrow]_class[0]_style[0]=ANGLE%20-19.595747561783185urlappend=%26unique_key%3D8dd3e319d1e111d892e2080020a0f4c9%26map.layer[textzoom03]%3DFEATURE+POINTS+1699114.16619+-120243.877124+END+TEXT+%22Saint-Jean-sur-Richelieu%22+END%26map.layer[textzoom46]%3DFEATURE+POINTS+1699114.16619+-120243.877124+END+TEXT+%22Saint-Jean-sur-Richelieu%22+END%26map.layer[arrowzoom03]%3DFEATURE+POINTS+1699114.16619+-120243.877124+END+END http://atlas.nrcan.gc.ca/auth/english/maps/topo/map?mapsize=525%20466mapxy=1700511.0503883713%20-122536.87132125527scale=2.00feature_na=Saint-Jean-sur-Richelieusearchstring=saint-jean-sur-richelieulayers=fapfeature%20nodata_ntdb_50k%20north_arrow%20other_features%20roads%20hydrography%20boundary%20builtup%20vegetation%20populated_places%20railway%20power_network%20manmade_features%20designated_areas%20water_features%20water_saturated_soils%20relief%20contours%20toponymy%20contourmap_layer[northarrow]_class[0]_style[0]=ANGLE%20-19.595747561783185urlappend=%26unique_key%3D8dd3e319d1e111d892e2080020a0f4c9%26map.layer[textzoom03]%3DFEATURE+POINTS+1699114.16619+-120243.877124+END+TEXT+%22Saint-Jean-sur-Richelieu%22+END%26map.layer[textzoom46]%3DFEATURE+POINTS+1699114.16619+-120243.877124+END+TEXT+%22Saint-Jean-sur-Richelieu%22+END%26map.layer[arrowzoom03]%3DFEATURE+POINTS+1699114.16619+-120243.877124+END+END regards /Pierre Béland / *De :* Pierre Béland *Date/heure :* 2011-05-24 18:59:16 *A :* HOT Openstreetmap *Cc :* talk-ca *Sujet :* [HOT] Flooding in Richelieu River, Quebec,Canada : Follow-up (Complement of information) Following are the ways and relation I have produced to document Richelieu River flooding. Affected zones (These will be revised when I obtain
Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec, Canada :Follow-up (Complement of information)
Very thanks to Sam Vekemans, Brent Fraser and Jean-Guilhem Cailton for their suggestions and help. Jean-Guilhem Cailton wrote on 201-05-27 The 30 m contour lines from tiles 031h03 and 031h06 (the shapefiles you gave), potentially connected to Richelieu river, have been imported, and put together in relation: http://www.openstreetmap.org/?relation=1602671 Jean-Guilhem, I will use this information for a basis of discussion, and see how it can reflect the flooded zones. Could you easily add to the relation, the 30m elevation for Missisiquoi Bay where Venise-en-Quebec town has been severely affected by floods? regards, Pierre Béland 2011-05-27 De : Jean-Guilhem Cailton Date/heure : 2011-05-27 05:19:54 A : Pierre_Béland Cc : Brent Fraser; HOT Openstreetmap; talk-ca Sujet : Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec, Canada :Follow-up (Complement of information) Hi Pierre, The 30 m contour lines from tiles 031h03 and 031h06 (the shapefiles you gave), potentially connected to Richelieu river, have been imported, and put together in relation: http://www.openstreetmap.org/?relation=1602671 Clearly, it is not enough to estimate the flooded zone, for which some kind of flow analysis would be needed, but maybe it can help in some areas, as you wrote. I used ogr2ogr -where ELEVATION=30 ... to extract the 30m contour line, and ogr2osm.py to convert it to .osm, for Josm. Best wishes, Jean-Guilhem Le 27/05/2011 06:30, Brent Fraser a écrit : Pierre, I can't comment on if the 30m contour solution is suitable, but if you want to extract the 30m contours, you could: 1. Use QGIS to extract 30m contour from *_FO.._1.shp files - load shapefile, Open Attribute Table, click on elevation field name to sort table by elevation value. - select all 30m values, click on Layer - Save selection as vector file. Save shapefile 2. Use converter (one of the ones on http://wiki.openstreetmap.org/wiki/Import/Shapefile) to create .osm files (I haven't tried this) 3. Use Josm to load osm files, tag, and update to OSM Best Regards, Brent Fraser On 5/26/2011 8:46 PM, Pierre Béland wrote: Many osm volunteers have worked in the last two days to correct roads, complete Canvec import and add street names. An other task is to estimate the flooded zone along the Richelieu River and Missisquoi Bay in Lake Champlain. One simple approach to determine the flooded zones would be to use the 30 meter contour line from Canvec data. This would be good at least for Richelieu River. These maps from Natural Resources Dept of Canada shows the 30 meter contour line. For the areas I visited last week with volunteers, this line delimits approximately the flooded zone. On monday 23, water level of the Richelieu river went up to approximately 30.8 meters in Saint-Jean-sur-Richelieu. Would it be a good solution to estimate the flooded zone ? If so, any idea, how we can extract 30 meter contour line from shape files using a tool such as Quantum GIS and convert to OSM ? ftp://ftp2.cits.rncan.gc.ca/pub/canvec/50k_shp/031/h/canvec_031h03_shp.zip ftp://ftp2.cits.rncan.gc.ca/pub/canvec/50k_shp/031/h/canvec_031h06_shp.zip Below is an example of Toporama map for Saint-Jean-sur-Richelieu, the wms version of Canvec, where we can see the 30 meter contour line. http://atlas.nrcan.gc. ca/auth/english/maps/topo/map?mapsize=525%20466mapxy=1700511.0503883713%20-122536.87132125527scale=2.00feature_na=Saint-Jean-sur-Richelieusearchstring=saint-jean-sur-richelieulayers=fapfeature%20nodata_ntdb_50k%20north_arrow%20other_features%20roads%20hydrography%20boundary%20builtup%20vegetation%20populated_places%20railway%20power_network%20manmade_features%20designated_areas%20water_features%20water_saturated_soils%20relief%20contours%20toponymy%20contourmap_layer[northarrow]_class[0]_style[0]=ANGLE%20-19.595747561783185urlappend=%26unique_key%3D8dd3e319d1e111d892e2080020a0f4c9%26map.layer[textzoom03]%3DFEATURE+POINTS+1699114.16619+-120243.877124+END+TEXT+%22Saint-Jean-sur-Richelieu%22+END%26map.layer[textzoom46]%3DFEATURE+POINTS+1699114.16619+-120243.877124+END+TEXT+%22Saint-Jean-sur-Richelieu%22+END%26map.layer[arrowzoom03]%3DFEATURE+POINTS+1699114.16619+-120243.877124+END+END regards Pierre Béland De : Pierre Béland Date/heure : 2011-05-24 18:59:16 A : HOT Openstreetmap Cc : talk-ca Sujet : [HOT] Flooding in Richelieu River, Quebec,Canada : Follow-up (Complement of information) Following are the ways and relation I have produced to document Richelieu River flooding. Affected zones (These will be revised when I obtain more detailed information on streets / areas affected. http://www.openstreetmap.org/browse/way/114705927 http://www.openstreetmap.org/browse/way/114705926 http://www.openstreetmap.org/browse/way/114705928 http://www.openstreetmap.org/browse/way/114706976 Boundary relation that could be used to produce Indexed map of streets with tools
Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec, Canada :Follow-up (Complement of information)
Dear Pierre, According to the shapefile data, Lake Champlain, and hence Venise-en-Québec are above the 30 m elevation. The shapefile contains punctual elevations of 31 m in this area (Plage Missisquoi, for example). The next contour line would be the 40 m one, but it does not look like it would be very useful for this. Best regards, Jean-Guilhem Le 27/05/2011 13:12, Pierre Béland a écrit : Very thanks to Sam Vekemans, Brent Fraser and Jean-Guilhem Cailton for their suggestions and help. Jean-Guilhem Cailton wrote on 201-05-27 The 30 m contour lines from tiles 031h03 and 031h06 (the shapefiles you gave), potentially connected to Richelieu river, have been imported, and put together in relation: http://www.openstreetmap.org/?relation=1602671 Jean-Guilhem, I will use this information for a basis of discussion, and see how it can reflect the flooded zones. Could you easily add to the relation, the 30m elevation for Missisiquoi Bay where Venise-en-Quebec town has been severely affected by floods? regards, /Pierre Béland / 2011-05-27 *De :* Jean-Guilhem Cailton *Date/heure :* 2011-05-27 05:19:54 *A :* Pierre_Béland *Cc :* Brent Fraser; HOT Openstreetmap; talk-ca *Sujet :* Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec, Canada :Follow-up (Complement of information) Hi Pierre, The 30 m contour lines from tiles 031h03 and 031h06 (the shapefiles you gave), potentially connected to Richelieu river, have been imported, and put together in relation: http://www.openstreetmap.org/?relation=1602671 Clearly, it is not enough to estimate the flooded zone, for which some kind of flow analysis would be needed, but maybe it can help in some areas, as you wrote. I used ogr2ogr -where ELEVATION=30 ... to extract the 30m contour line, and ogr2osm.py to convert it to .osm, for Josm. Best wishes, Jean-Guilhem Le 27/05/2011 06:30, Brent Fraser a écrit : Pierre, I can't comment on if the 30m contour solution is suitable, but if you want to extract the 30m contours, you could: 1. Use QGIS to extract 30m contour from *_FO.._1.shp files - load shapefile, Open Attribute Table, click on elevation field name to sort table by elevation value. - select all 30m values, click on Layer - Save selection as vector file. Save shapefile 2. Use converter (one of the ones on http://wiki.openstreetmap.org/wiki/Import/Shapefile) to create .osm files (I haven't tried this) 3. Use Josm to load osm files, tag, and update to OSM Best Regards, Brent Fraser On 5/26/2011 8:46 PM, Pierre Béland wrote: Many osm volunteers have worked in the last two days to correct roads, complete Canvec import and add street names. An other task is to estimate the flooded zone along the Richelieu River and Missisquoi Bay in Lake Champlain. One simple approach to determine the flooded zones would be to use the 30 meter contour line from Canvec data. This would be good at least for Richelieu River. These maps from Natural Resources Dept of Canada shows the 30 meter contour line. For the areas I visited last week with volunteers, this line delimits approximately the flooded zone. On monday 23, water level of the Richelieu river went up to approximately 30.8 meters in Saint-Jean-sur-Richelieu. Would it be a good solution to estimate the flooded zone ? If so, any idea, how we can extract 30 meter contour line from shape files using a tool such as Quantum GIS and convert to OSM ? ftp://ftp2.cits.rncan.gc.ca/pub/canvec/50k_shp/031/h/canvec_031h03_shp.zip ftp://ftp2.cits.rncan.gc.ca/pub/canvec/50k_shp/031/h/canvec_031h03_shp.zip ftp://ftp2.cits.rncan.gc.ca/pub/canvec/50k_shp/031/h/canvec_031h06_shp.zip ftp://ftp2.cits.rncan.gc.ca/pub/canvec/50k_shp/031/h/canvec_031h03_shp.zip Below is an example of Toporama map for Saint-Jean-sur-Richelieu, the wms version of Canvec, where we can see the 30 meter contour line. http://atlas.nrcan.gc. ca/auth/english/maps/topo/map?mapsize=525%20466mapxy=1700511.0503883713%20-122536.87132125527scale=2.00feature_na=Saint-Jean-sur-Richelieusearchstring=saint-jean-sur-richelieulayers=fapfeature%20nodata_ntdb_50k%20north_arrow%20other_features%20roads%20hydrography%20boundary%20builtup%20vegetation%20populated_places%20railway%20power_network%20manmade_features%20designated_areas%20water_features%20water_saturated_soils%20relief%20contours%20toponymy%20contourmap_layer[northarrow]_class[0]_style[0]=ANGLE%20-19.595747561783185urlappend=%26unique_key%3D8dd3e319d1e111d892e2080020a0f4c9%26map.layer[textzoom03]%3DFEATURE+POINTS+1699114.16619+-120243.877124+END+TEXT+%22Saint-Jean-sur-Richelieu%22+END%26map.layer[textzoom46]%3DFEATURE+POINTS+1699114.16619+-120243.877124+END+TEXT+%22Saint-Jean-sur-Richelieu%22+END%26map.layer[arrowzoom03]%3DFEATURE+POINTS
Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec, Canada :Follow-up(Complement of information)
Jean-Guilhem Cailton wrote on 2011-05-27 According to the shapefile data, Lake Champlain, and hence Venise-en-Québec are above the 30 m elevation. The shapefile contains punctual elevations of 31 m in this area (Plage Missisquoi, for example). The next contour line would be the 40 m one, but it does not look like it would be very useful for this. This is exact. The 40 meter contour line is not usefull for us. Thanks Jean-Guilhem. Pierre Béland ___ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca
Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec, Canada :Follow-up(Complement of information)
Bonjour tous le monde, I have generated a 30m and 31m contour lines for Richelieu river and lake Champlain (using SRTM data). It fits the 30m contour provided by Jean-Guilhem but doesn't seem to fit pretty well the flooded wetland area provided by Pierre. Any idea if this data can be used (usgs licence point of view)? And if it can be usefull? Daniel _ From: Pierre Béland [mailto:infosbelas-...@yahoo.fr] Sent: May-27-11 12:40 To: HOT Openstreetmap Cc: talk-ca Subject: Re: [HOT] [Talk-ca] Flooding in Richelieu River, Quebec,Canada :Follow-up(Complement of information) Jean-Guilhem Cailton wrote on 2011-05-27 According to the shapefile data, Lake Champlain, and hence Venise-en-Québec are above the 30 m elevation. The shapefile contains punctual elevations of 31 m in this area (Plage Missisquoi, for example). The next contour line would be the 40 m one, but it does not look like it would be very useful for this. This is exact. The 40 meter contour line is not usefull for us. Thanks Jean-Guilhem. Pierre Béland ___ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca
Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec, Canada :Follow-up(Complement of information)
2011/5/27 Daniel Begin jfd...@hotmail.com: Bonjour tous le monde, I have generated a 30m and 31m contour lines for Richelieu river and lake Champlain (using SRTM data). It fits the 30m contour provided by Jean-Guilhem but doesn't seem to fit pretty well the flooded wetland area provided by Pierre. Any idea if this data can be used (usgs licence point of view)? And if it can be usefull? SRTM is USGov-PD. It is probably most-useful as a separate layer to displayed over other / better / different data. That keeps it out of OSM; keeps the origin clear; and make it easy to combine as desired with other data. It would be hacky to publish the 30m, 31m, etc. topo lines as gpx, but it would make mashing them up in OpenLayers or on various other maps pretty easy. Example and tutorial: http://weait.com/content/easy-osm-your-gpx-tracks ___ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca
Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec, Canada :Follow-up(Complement of information)
Daniel, The SRTM data has 90m cell size, while the CDED (from the Geobase site) has 30m cells (and 1m height resolution) which might rendered better contours. Best Regards, Brent Fraser On 5/27/2011 11:52 AM, Daniel Begin wrote: Bonjour tous le monde, I have generated a 30m and 31m contour lines for Richelieu river and lake Champlain (using SRTM data). It fits the 30m contour provided by Jean-Guilhem but doesn't seem to fit pretty well the flooded wetland area provided by Pierre. Any idea if this data can be used (usgs licence point of view)? And if it can be usefull? Daniel *From:*Pierre Béland [mailto:infosbelas-...@yahoo.fr] *Sent:* May-27-11 12:40 *To:* HOT Openstreetmap *Cc:* talk-ca *Subject:* Re: [HOT] [Talk-ca] Flooding in Richelieu River, Quebec,Canada :Follow-up(Complement of information) Jean-Guilhem Cailton wrote on 2011-05-27 According to the shapefile data, Lake Champlain, and hence Venise-en-Québec are above the 30 m elevation. The shapefile contains punctual elevations of 31 m in this area (Plage Missisquoi, for example). The next contour line would be the 40 m one, but it does not look like it would be very useful for this. This is exact. The 40 meter contour line is not usefull for us. Thanks Jean-Guilhem. Pierre Béland ___ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca ___ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca
Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec, Canada :Follow-up(Complement of information)
Hi all, I've tried to put my boots on the ground without going there !-). I found a pretty clear satellite image of the river at its max level (30-31m) - which doesn't really changed since ... http://earthobservatory.nasa.gov/NaturalHazards/view.php?id=50577 I made few geometric adjustments to the image and compare the result with 30m GeoBase and SRTM contours. Geobase contours gives better results between St-Jean and L'Île aux Noix but from there to the US boundary, neither GeoBase nor SRTM is right. I'm trying to produce a flooded area from DEM data while I'm looking at an image that contains what I'm looking for - the flooded area! Why not mapping from it? I understand the image can be used - http://earthobservatory.nasa.gov/ImageUse/ Any idea on how I can use this GeoTiff image in JOSM? Cheers, Daniel _ From: Daniel Begin [mailto:jfd...@hotmail.com] Sent: May-27-11 15:18 To: 'Brent Fraser' Cc: 'HOT Openstreetmap'; 'talk-ca' Subject: Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec,Canada :Follow-up(Complement of information) Bonjour Brent, Which one is better in this situation, SRTM or GeoBase? I would prefer SRTM for the following reasons... SRTM has 90m cell size but the data in each cell are real elevation - including roof tops and crop height !, Geobase has 30m cell size but the data in each cell is an interpolation between adjacent contour interval from 50K map. So, in flat/low hills areas, SRTM will give a much better idea of the height than Geobase. For example, a 8m hill, standing between elevation 31m and 39m won't be visible in Geobase data. Same reasoning for a steep cliff, and so on... Furthermore, I suspect that using the 30m contour from SRTM might be valid for St-Jean-Sur-Richelieu area but the 31m should probably be used near Lake Champlain. In this case I would quote James Ewen, You need to Put your boots on the ground to decide which one is valid !-) I'm also looking at converting this into .gpx format as proposed Richard Cheers, Daniel _ From: Brent Fraser [mailto:bfra...@geoanalytic.com] Sent: May-27-11 14:19 To: Daniel Begin Cc: 'Pierre Béland'; 'HOT Openstreetmap'; 'talk-ca' Subject: Re: [Talk-ca] [HOT] Flooding in Richelieu River, Quebec, Canada :Follow-up(Complement of information) Daniel, The SRTM data has 90m cell size, while the CDED (from the Geobase site) has 30m cells (and 1m height resolution) which might rendered better contours. Best Regards, Brent Fraser On 5/27/2011 11:52 AM, Daniel Begin wrote: Bonjour tous le monde, I have generated a 30m and 31m contour lines for Richelieu river and lake Champlain (using SRTM data). It fits the 30m contour provided by Jean-Guilhem but doesn't seem to fit pretty well the flooded wetland area provided by Pierre. Any idea if this data can be used (usgs licence point of view)? And if it can be usefull? Daniel _ From: Pierre Béland [mailto:infosbelas-...@yahoo.fr] Sent: May-27-11 12:40 To: HOT Openstreetmap Cc: talk-ca Subject: Re: [HOT] [Talk-ca] Flooding in Richelieu River, Quebec,Canada :Follow-up(Complement of information) Jean-Guilhem Cailton wrote on 2011-05-27 According to the shapefile data, Lake Champlain, and hence Venise-en-Québec are above the 30 m elevation. The shapefile contains punctual elevations of 31 m in this area (Plage Missisquoi, for example). The next contour line would be the 40 m one, but it does not look like it would be very useful for this. This is exact. The 40 meter contour line is not usefull for us. Thanks Jean-Guilhem. Pierre Béland ___ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca ___ Talk-ca mailing list Talk-ca@openstreetmap.org http://lists.openstreetmap.org/listinfo/talk-ca
