nadar

Hello, I'm back after a few difficult months.... could you please reactivate my account. Thanks

Hello could you please re-activate my status ? Thanks

Is there a possibility to find the location of a image extracted from Google Earth ? I received a few images obtained by screen copy of Google Earth. The scale bar is included in the image, but not the coordinates nor the orientation (I assume it's North up). I only have a vague indication of the region. Is there a solution to analyse the GE database using some image matching algorithm ?

If the subject doesn't move too much (no wind on the leaves, etc.) and the camera is fixed, it will probably work, but don't expect extraordinary results (because of the ultrawide lens, resolution is lower on the border of the images. If the subject or camera are moving (including vibrations), then the rolling shutter will be a severe limitation. For a serious project, I will rather use a compact camera with a "normal" lens and a global shutter.

If you use spectral properties to classify, they should be as pure as possible. Visual interpretation using your brain is much more sophisticated than any computer-based classification, because it constantly switch between a local analysis (mainly texture and shape) and a global analysis (scene structure). Having a (big) computer slowly driving a car (in moderate traffic and on good roads with plenty of road signs) is one thing. Driving madly a junk car in Instambul traffic jams is another story. I'm not saying a computer is always more stupid than a turkish taxi driver, but as far as scene analysis is concerned, I will not put a penny on the machine...

This one works: http://www.asprs.org/a/society/committees/standards/ASPRS_Positional_Accuracy_Standards_Edition1_Version100_November2014.pdf

"error 404. Not Found. Sorry, but that page is lost." Any idea, ?

I fully agree with dr_s1ngh

I tried. I only found a solution to put all selected points to the same elevation, but not to add or remove the same value to each individual point (to rise up a roof for instance) May be I shoud try exporting a portion of the cloud and reimporting it at another position ?

I'm looking for a solution to modify the elevation of selected points in a .LAS or .PLY points cloud. I want to simulate an increase or decrease of the height of selected objects (trees, buildings, etc.). I dont want to change their colour. The ability to move a selected group of 3D points would also be useful. I know how to do this in a mesh generated from the cloud, but I have to fully preserve the details of the cloud. can somebody share some ideas or indicate a software compatible with these requirements ? Thank you in advance

I agree with you, on some satellites, the difference of resolution between pan and multispectral becomes ridiculous. Keep in mind that a ration 1:4 means you get 16 Pan pixels for one multispectral ! High contrast objects completely "smear" on the neighbours. I understand for marketing reasons, producers want to announce the highest figures, but.... I'm not even talking about the effective resolution of these images. If you want, you can resample a Landsat TM image to 10 cm ! I don't thin an algorithm will be able to reconstruct high res multispectral images suitable with classification. If the information is not there, you will never reconstruct it. On the same mood, you could also publish a movie captured with your cell phone on a Blu-Ray disc. It's feasible, but the results... If your classification is mainly based on spectral properties (e.g. agriculture), I will rather work on pure spectral bands only. If recognition is more based on shape and structure, Pan-sharpening may help. I would rather use pan sharpened images for visual interpretation only.

Thanks a lot. I have some readings for a while. I will come back later

In Montana, I think you can upload your own raster maps ("custom maps"). I did it, but the management of memory is not very efficient, and as soon as you get a few maps, you get 'insufficient memory" errors, even if you have plenty room on your memory card. Global Mapper has interesting possibilities to export either vector data or raster maps to Garmin devices

Does somebody have a good reference on - practical results of DEM generation using various types of satellite imagery - the relation (if any) between spatial resolution) and the accuracy (in elevation) for derived DTM/DSM - the same question about airborne LiDAR data (relation between points density and accuracy). (I'm preparing a project where DEM accuracy is critical (flooding) and we are hesitating between satellite and airborne LiDAR All advices and experience are welcome !

Publishing such info without a price tag is useless and quite stupid. Users are not cows waiting to be milked.

Very compact motion and position sensor. It uses a MEMS inertial system (INS) to measure angles and accelerations combined with a GPS to measure positions and speed. Xsens MTI-G-700 (purchased in march 2013) specs: http://shop.xsens.com/shop/mti-g-100-series/mti-g-700-gps-ins/mti-g-700-gpsins-2a5g4-dk Provided with software development kit and carrying case Connection to PC via USB cable (4m length) GPS antenna with strong magnetic mount: cable length 3+5 m size: 58x58x22 mm. Weight 58g. Software: MTmanager (provided with full licence and recent updates) is used to graphically display in real time the position of the sensor(in 3D), its orientation (omega,phi,kappa angles, speed and acceleration data. The software is also used to record all these data (or only selected ones), at a user selected frequency (up to 100 records per second), in a wide variety of output formats, including user-defined ones. Possible uses: - motion tracking (sports, health, etc.) - Automobile and mechanical tuning (analysis of speed and longitudinal/lateral accelerations on different places of a circuit) - Avionics and UAVs - Photography and video - Monitoring of construction, earthmoving engines and floating machinery - etc. (I used it for photogrammetry) I'm selling it 2000 € (=50% of the price af a new one). I'm selling it because I don't use it anymore. It was used about 12 times and works pertfectly. I prefer hand delivery against cash payment. This allows me to give a demo and a short tutorial of the software (configuration is not very easy) I can do this at my place (Huy, Belgium) or around Liège, Namur or Brussels. Other solution to be negotiated. Parcel shipment is also possible (afterPaypal payment), but at your own cost (from Belgium) and under your full responsibility (insurance recommended). (The parcel will weight approx. 1 kg) Please contact me by MP to obtain more details

It can be also a "normal" tourism map with "shadowed relief" (I did one a few years ago for Namibia: http://www.nadar-gis.com/nadar/html_en/applications-cartotourist-1a.htm Basically, it's a SRTM DEM. Shadows are generated in Global Mapper. Map editing done in ArcGIS and map sheet editing in Illustrator

But barometric elevation readings are also given in a specific reference system, WGS84 elliposid, WGS84 corrected or anything else. If your gps is set on WGS ellipsoid, you will read "Z+40m" when actually standing on the ground. Not a good new if you are skydiving...

I think Garmin GPSes use a modified WGS84 datum, to correct for the difference between the ellipsoid and the geoid. My problem is to know the parameters of this correction. On the GPS of my Nexus 7 tablet, you can select either ellipsoid or geoid elevation, and playing with this option highlights the difference between both system. The problem is related to the fact that this correction is 1) not documented, 2) not the same for all brand/model. In my view, when data are documented as "WGS84" referenced, it should implicitely be "WGS84 Elliposoid". If a correction is added, then it's no more "WGS84", but somethink like "WGS84 bis", "WGS84 corrected" or anything similar.

I saw that. Seems a little bit complicated for me ;-( I don't need to understand the maths behind projections and datums. Just need to use a simple GPS and get about 0 elevation reading when I'm sailing on a boat, not +40m...

WGS84 is used by most GPS, and became a de-facto standard, but it is not always easy to use: As far as I'm informed, different versions of WGS84 datum exist. Originally (1986 ?), the elevation reference was an ellipsoid (defined by a few mathematical parameters such as the length of 3 axes, the position of the center, etc.) . Accordingly, important differences existed between elevations read on the GPS (reference level = ellipsoid) and actual elevation (read on a topo map or seen on a coast line or a boat) (reference level = mean sea level). Apparently, later implementations of WGS84 added some correction to better fit to the actual world. AFAIK, these corrections were implemented in the form of a look-up table defining discrete Z-corrections values according to longitude and latitude position on a grid. (contrary to an ellipsoid, a a geoid cannot be described by a few math parameters). Apparently multiple implementations of this correction exist. Unfortunately, most (basic) GPSes still document it as "WGS84". Comparing measurements doneon the same place with different GPSes can give very different results (for elevation). In my place; up to 40m. My questions to the community: 1) can you confirm my interpretation ? 2) how can you determine which WGS84 flavour you are using 3) is there an easy solution to correct this ?

I'm producing oriented blocks from digital SLR camera combined to a GPS + IMU mems sensor. The aim is to measure trees size (crown diameter and height) for biomass estimation. Image resolution is about 15cm. The blocks are quite small (3-10 images in a single row, with 70% overlap) For one project, it's nearly impossible to obtain accurate GCPs (high density tropical forest), and satellite images are not very good (clouds / haze): I have to rely on GPS / IMU only ("direct georeferencing") The resulting oriented photos (and orthophotos) are quite good and coherent, but are misplaced for 30-50 m. Is there a solution to interactively shift the entire oriented block to better match a reference satellite image, using only one reference point ? I can of course shift the resulting orthos, but then I lose the possibility of 3D analysis. I'm using ERDAS 2013 and ArcGIS 10, with all extensions. Thanks for your suggestions

Had the same symptoms. Tried a million solutions (including reinstalling software and OS :-( ...) to discover that starting with a new .mxd fixed it...

There was a free utility (from Mentor Software) called GeoTiffExaminer, to copy the georeferenciation info from GeoTiff to world file and back. Apparently, it is no more available for download. Keep in mind that georef is related to upper-left corner of your image. If you resize or crop it, the reference is no more valid !