Elevation data
Hello guys, which vertical and horizontal resolution has the default World_Base_Relief.cwdem map ?
Is it possible to load LIDAR data (es.SONNY's LiDAR DTM) which are arranged in several .hgt tiles ?
many thanks
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Hello,
"default World_Base_Relief.cwdem map" : very bad résolution, 90m (3") or more...
"Is it possible to load LIDAR data (es.SONNY's LiDAR DTM) which are arranged in several .hgt tiles ?"
Yes, but not directly, you have to convert them.
Tell us for which country?.HGT Sonny (which are not all from LiDAR measurements) generally have a horizontal resolution of 1" arc (approximately 25m/30m). For France, you can have DEMs with a resolution of 5m, available via the Twonav site directly.
Best regards,
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Hello,
Yes,
Import data from Sony, then with Land you ca merge the tiles dans une carte des relief *.cdem.
Other solutions are also available:
- Somes DEM precise file are available to be loaded on official geographic of some contry (Ex, Belgium, Switzerland, French)
- The sofware tool QGIS, available in Open Source provides solution to works with thoses data. (Cut a zone, Merging tiles, Move the coordinates , extract curves)
- For frenchs users this Web Site provide TwoNav DEM computed from IGN officials data (Very precise) https://rando.tybern.fr/telechargements/MNT/
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I haven't used Land for many months to create a DEM from SONY, but I did and it works.
Now I use QGIS
Qgis view , in black / withe the DEM , and the extracted curves
The curve (Land Screen Shot) in a Map
This TwoNav French DEM is computed with Land with SONY Data
This TwoNav Belgium DEM is computed with Land with SONY Data. Land do not provide tu cut Sony Tiles
Belgium Lidar DEM 1m x 1m x 1 m, avaialble on Wallonnia IGN Web site
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Hello Thierry CHARLÈS, Yuou said: "Import data from Sony, then with Land you can merge the tiles dans une carte des relief *.cdem. "
But how can I do this? If I Open all the .hgt as a map with Land 8.9.7 and try to do "merge maps" I get an error "this option lets You save several maps as only one. To do so you have to load previously more than one map".
Maybe .hgt are not considered as maps ?
After that I saw that I can right click on each .hgt and do save relief" as .cdem, but I didn't find a way to merge them into one.
Tomorrow I will try with Qgis but doing it in Land should be preferred
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Hello,
There is this tutorial which dates from the time when access to the SONY site was different, for the procedure I think it is still relevant today.
It's in French, ask Google (or your PC) to translate.
https://blog.utagawavtt.com/fr/blog/comment-installer-mnt-gps-twonav
With a little curiosity, on this site you can consult other useful tutorials for TwoNav GPS.
Best regards
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Hello
Utilisation des "cdem", lorsque votre CDEM est issus de tuiles obtenues du site SONY les tuiles sont relativement grandes (exemple dans le tutoriel la tuile de relief ouest de la Suisse se prolonge assez loin en France) c'est un avantage pour les activités transfrontalières. Par contre il y a un artefact important, vous pouvez ouvrir ou charger plusieurs CDEM dans Land ou votre GPS, ils sont gérer par ordre de présence dans l'arbre des cartes le plus haut est celui actif. Donc si vous en avez plusieurs de sélectionner et que vous suivez une activité assez loin de la frontière de votre pays il n'est pas impossible que vous puissiez traverser un autre CDEM (Un bord, un coin, etc..), or sur les bords il exite une bande a - 9999m. Au cours d'une activité si vous constez des altitudes diaboliques, la cause sera que vous traversez un bord ou un coin de la carte du relief voisin de votre terrain de jeu. Cela m'est arrivé il y a quelques années alors que je faisait un Trail a plus de 200 km de la frontière c'était le coin d'une dalle de relief. N'oubliez pas que le relief du CDEM est celui du sol, donc pour tout franchissement de pont, de tunnel ou dans le flanc abrupte d'un massif montagneux les altitudes ne seront pas celle du contact de vos pieds avec la terre.
Bonnes balades.
Best regards
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The default World_Base_Relief.cwdem map has a horizontal and vertical resolution of 90 meters, and yes, you can load LIDAR data like SONNY's LiDAR DTM arranged in .hgt tiles.
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