• Napoleon Eduardo Cornejo added an answer:
    Which software is more suitable to perform a orthorectification on TerraSAR-X ScanSAR MGD imagery? I'm using PCI and getting really bad results.
    This is the result I get - a distorted/asymetric scene with a lot of white "N/A" dots.
    The funny thing is that for Radarsat-2 the results are clean and done, perfect.
    Anyone know how to fix it, or an alternative software to perform an orthorectification?
    Napoleon Eduardo Cornejo · Delft University Of Technology

    I have been trying to work with ScanSAR SSC data from Terrasar in NEST, and it does not work.  the bands are always kept separate and cannot be put together properly.

  • John W. Kern added an answer:
    Does it make sense to assess uncertainty in climate change impact projections?
    It is now widely admitted that climate change impacts on water resources are occurring and are expected to amplify in the future. However, these impacts are highly uncertain and usually scientist and decision makers prefer to have a quantitative assessment of these associated uncertainties. How can we assess future uncertainty related to climate change in the absence of observations? Then, how can decision makers consider these uncertainties in their future plan management of water resources for instance?
    John W. Kern · Kern Statistical Services, Inc., University of Wyoming, Montana State University

    @roger-- I agree with your points strongly.  Often the parameters being simulated are strongly correlated, whereas most canned routines for generating distributions allow them to vary independently. This nearly always results in gross overstatement of the output uncertainties.  Useful models for uncertainty distributions including reasonable dependencies among model inputs are difficult to develop, but highly useful when achieved.

  • Jan J Quets added an answer:
    Does anyone have examples of works, researches, or publications on digital mapping from UAV?

    I know that UAVs are one of the most important innovation of the last years in geomatic and I know that with these systems it is possible to obtain 3D models and orthoimages with high levels of detail and accuracy, but I know very few examples about the use of UAV in digital mapping, mainly to produce topographic maps.

    Does anyone have information on this specific topic?
    What could be the scale of the topographic maps?
    What could be the size of the area to be surveyed?
    What are the differences between fixed-wing and multi-rotor for these applications?

    Many Thanks


    Jan J Quets · University of Antwerp

    Dear Professor Lo Brutto,

    Uptill now I performed four field campaigns with a helikite, and two other with a multi-rotor drone. In a recent publication I made an orthoimage with a UAV (1cm resolution), and I just finished a manuscript (which I'm submitting soon) in which I made a detailed topographic map of about 20 ha with a multirotor UAV.

    the scale of these maps: it's simple, the lower the altitude of the UAV, the higher the resolution, the larger the scale of your imagery.
    However, with low-altitude flights, the speed of the UAV should be decreased (or the shutter speed increased, if the light conditions allow it) to avoid blurry images, and here comes the difference between fixed-wing and multi-rotor. The fixed-wing has a minimum speed, and therefore puts a constraint on the resolution of the imagery (but the fixed-wing is more efficient in terms of battery consumption with respect to the multi-rotor).

    the size of the area to be surveyed: much is possible, but of course, it depends on the time you have available. It took me 3 hours to capture a 20 hectare field with 1 cm/pixel resolution (UAV altitude about 20 m), with a multi-rotor drone, but before that we had to place the ground control points and measure their coordinates with a total station (which also took nearly 2 hours with 2 or 3 people).

    Thus, the lower the image resolution you want, the less time it will take to photograph a certain area because your UAV can fly higher (which decreases its total flight distance to cover the area) and faster while still getting sharp pictures. You also should keep in mind that batteries have limited energy (for they had to be changed and recharged about every 30 minutes, in our case), and that one is usually not allowed to control its UAV beyond a certain radius from yourself, depending on the license you have (in our case 500m)

  • Joe Mccollum added an answer:
    How can space debris be measured aside from just tracking them?
    Space debris include space junk, space waste and defunct objects in orbit around Earth. It includes spent rocket, old satellites and fragments and they pollute space. They usually can be tracked, but how about measuring their quantity and relating the values to threshold limits?
    Joe Mccollum · US Forest Service

    Putting a reentry motor on every space shuttle tile that flicks off would not be practical.

  • Andrei Mîrț added an answer:
    Do you have information about national projects of LIDAR and photogrammetric missions in your country?
    I am looking for data description, links to data browsers including data collected by national institutions in other countries over the worlds.

    What are their parameters?
    How often they are collected usually?
    Is there any official data browser?

    For example, in Poland, ​​LIDAR of whole country with an average density of 4p/m2 and 12 p/m2 (for big cities) has been almost collected (90%). Link to the availability of data (DSM, DTM, LAS datasets)
    Aerial photos are obtained every 2-3 years for whole country with a resolution of 10 cm (for big cities) and 25 cm or 50 cm for agricultural regions (depending on the size of real-estates) Link:

    I'll be grateful for the assistance and support information about situation in your countries.
    Andrei Mîrț · Wageningen University

    For the Netherlands, there is AHN.

    You can find all information and download links here:

    Though it's easier to access the data through or through their qgis plugin also called pdok viewer.

    As far as I know they redo it every three years.

  • Fabio Zottele added an answer:
    How to make soil Maps from point data?
    I have 100+ point data of soil type, for example at point x soil is "clay", at point y soil is "clay-sand", at point z soil is "sand" and so on. Now i want to generate soil map/surfaces. Kindly help me if anyone has some solution, suggestions or free software.
    Fabio Zottele · Istituto Agrario di San Michele all’Adige (IASMA), Fondazione Edmund Mach

    Pay attention for some soil variables that are compositional (particle size fractions). Take a look here ( and here (

  • Mohamed El Mehdi Saidi added an answer:
    Free digital terrain model (DEM) on the web

    is it possible to find on the web free maps of the digital terrain model (DEM) with more detail than 30 meters resolution. Thanks.

    Mohamed El Mehdi Saidi · Cadi Ayyad University

    Ok, thanks and best regards

  • Nina Heiska added an answer:
    Can anyone tell me where I can download the free full waveform experimental LIDAR data?
    I need some full waveform experimental LIDAR data.
    Nina Heiska · Aalto University
    There is some sample data here
  • Ana-Maria Ciobotaru added an answer:
    Has anyone checked the accuracy of freely available datasets on the web?
    Nowadays, lots of geospatial data is available on the World Wide Web that can be explored, exploited and consumed for free. Is this data accurate enough? Has anyone tested its horizontal/vertical accuracy? These are the questions which might be of interest to many of us.
    Ana-Maria Ciobotaru · University of Bucharest
    I have also the same question and I have put here on RG. That was abou the data of lans use - land corine - CLC.
  • Ireneusz Baran added an answer:
    What are the methods for 3D City Modeling and which one is best?
    I want to understand the various methods used for 3D city modelling and their advantage, disadvantage.
    Ireneusz Baran · Curtin University Australia

    CityMGL and I would use some imagery based method (pictometry based perhaps?) rather than LiDAR unless CityGML LOD1 is good enough. If you need to create CityGML model LOD2 or higher I don't think there are automatic methods to do it. Semi automatic method is the way to go right now. Plenty of scope for research here.

  • Ismail Önden added an answer:
    What is the persentage of data used by managers and decision makers that it is related geographically today at global scale?
    Around 1991, Les. Worral has informed us that "more than 80% of data used by
    managers and decision makers is related geographically". Back then, at the very early days of world wide web (WWW), with the absence of smartphones and Location Based Services (LBS) such news signified the important contribution of geograpfical thinking and relationships of data used by decision and policy makers. Today, after 23 years of major advances of internet with cloud computing and using real-time web-gis servers and geospatial modules, with availability of qualitative Open-Source software and web-services, is it possible to estimate the geographical relation of data used by managers and decision makers at a global scale? Is there existant such a research approach?
    Ismail Önden · Okan Universitesi
    when i read the question, i remembered the tobler's law: "everything is related to everything else but near things are more related than distant things".

    i remember the recent publications for empirical proofs for the first law of the geography. these researchs might help to find answers of your question.
  • Jasim Ali added an answer:
    How can we get 3D urban surface materials by remote sensing?
    I am thinking of working on building a 3D model with the characteristics of urban materials using remote sensing data. Could you please suggest any approach or possible image combination for that? As this model needs 2d images with elevation, the challenge still is how to get the vertical objects' material types (such as walls).
    Jasim Ali · University of Nottingham
    no it does not, I need to build a 3D or 2.5D for a hole city
  • Dieu Tien Bui added an answer:
    What are the best iPad/Android Apps for GPS tracking and geology?
    Tell me about the apps you can’t live without
    Dieu Tien Bui · Telemark University College
    Could try iGeoTrans
  • Arun Kumar added an answer:
    How can I calculate sediment yield using Universal Soil Loss Equation (USLE)? and what input data require in using USLE?
    I want to estimate the soil loss for my study area but there are lots of confusion. USLE require rainfall erosivity factor, soil erodibility factor, topographic factor, crop management and conservation practice factor and I am unable in getting these factors.
  • Peter Mwangi added an answer:
    What is the minimum acceptable sample size in AHP when you have 13 variables under consideration?
    I have a range of experts but I am not sure how many questionnaires I should run.
    Peter Mwangi · Jomo Kenyatta University of Agriculture and Technology
    Elaborate the likert scale
  • Prabu Dheenathayalan added an answer:
    What is the standard difference between DTM, DSM and DEM especially with respect to the fast-changing geospatial semantics?
    These three terminologies can be confusing. Please shed more light.
  • Kris Nackaerts added an answer:
    How can I import and process MODIS EVI Data from MODIS Data set (8 day period combined product ) using open source GIS softwares?
    The data is available in HDF format.
    Kris Nackaerts · Flemish Institute for Technological Research
    A nice tool for MODIS data =
  • Iyyanki Muralikrishna added an answer:
    How far can one accept that the map scale in a digital GIS domain is irrelevant?
    How can we ignore the scale either for map data collection or map data analysis. In Geospatial mapping and modelling, it is well known that the scale of the map is the most common form of information content measurement as referred to by users. Because a map scale gives an idea of the content as well as depth of information.
    Iyyanki Muralikrishna · Former Adjunct Professor Asian Institute of Technology, Bangkok, Thailand
    Thank you for the answer. I agree with what has been stated
  • Paul Ouma added an answer:
    Can anybody provide a list of all the available software packages for Precise Point Positioning (PPP) technology?
    Paul Ouma · Jomo Kenyatta University of Agriculture and Technology
    Try this
    RTKLIB, its an opensource software and easy to use
  • Alberto Blanco added an answer:
    Do you have any suggestions/comments on the new online version of the Habsburg Second Military Survey (1806-1869) maps?
    Our project about to geo-referring and web publishing of the whole Habsburg Second Military Survey, covering Austria, Hungary, Czech Rep, Slovakia, Slovenia, Croatia, parts of Ukraine, Poland, Romania, Italy, Montenegro and Serbia is finished, result is here:
    We'd be happy to hear any suggestions for further improvement of the page and the database, which is open to the scientific community.
    Alberto Blanco · University of Alcalá
    Balazs, this is exactly what I was asking. I considered very important trying to develop a lot of environmental studies (environment because is my theme) using the maps as reference. We are doing something "similar" in the Madrid Region in Spain.

  • Huang Jinlong added an answer:
    Does anyone have the erdas or envi model for the geostatistical neighborhood similar pixel interpolator?
    I am comparing methods for data filling for Landsat ETM+ SLC-off
    Huang Jinlong · Nanjing University
    You can download it from here -->
  • Abhilasha Kumari added an answer:
    In ERDAS how can we convert the classified images into the grid?
    For plotting spatial metrics we have to classify the temporal images and then we have to convert it into grid and then input it into fragstat tool. But I am not getting how to convert the classified images into the grid in Erdas or any other software. Please suggest how to convert the classified images into the grid?
    Thank you all. Really i try in erdas and arcgis also, it worked..thanks all
  • Richard Gloaguen added an answer:
    How can you use rapid eye images and landsat in biomass study when the rapid eye images only cover certain areas of your whole study area?
    The high resolution rapid eye images cover 4 villages of a whole district which is the study area.
  • Wendy M Griffiths added an answer:
    What are the best institutions to study Remote Sensing for pasture and natural grasslands worldwide?
    I am looking for a place to send a student to spend about six months developing a research project in this thematic area
    Wendy M Griffiths · DairyNZ
    If the student wants an experience downunder - Ian Yule at Massey University, NZ
  • Cristina Radnea added an answer:
    How can one orthorectify LISS-4 MX data in Erdas Imagine?
    To orthorectify any image RPC file is needed. How to obtain RPC file for LISS-4 data?
    Cristina Radnea · National Research and Development Institute for Soil Science, Agrochemistry and Environmental Protection
    I don't think it will work, but try to put this question to the data provider; he is from your country, isn't he ?
  • Richard James Telford added an answer:
    Fitting variogram model with NLS in R
    I tried to compare the result obtained by fitting the spherical variogram model using fit.variogram and nls functions. The large difference in the results is a great concern for me knowing that the two functions use Weighted Least Squares (WLS) approach for estimating parameters. The steps taken are as follows: ## Fit empirical semivariogram using gstat empvar<-variogram(yield ~ 1,canmod.sp,cutoff= 400,width = 25, Cressie=TRUE) # Fitting Spherical variogram model to sample variogram sph.var<- vgm(psill =130, model = "Sph", range = 65, nugget = 180) sph.mod<-fit.variogram(empvar, model = sph.var) print(sph.mod) The result obtain from fitting the spherical model to sample variogram is sph.mod model psill range 1 Nug 230.917736411 0.0000000000 2 Sph 108.323055319 87.6889385431 The non-linear least squares (NLS) approach use by default s Gauss-newton algorithm in an iterative search process. I used the initial values obtained from the empirical variogram above (psill=130, range=65, and nugget=180) as starting values for the iterative procedure. ## Define Spherical Variogram functions for NLS sph.vgram <- function(dist, range, psill, nugget){ dist <- dist/range nugget + psill*ifelse(dist < 1, (1.5 * dist - 0.5 * dist^3),1) } ## Fitting spherical with NLS fit.var <- nls(gamma~sph.vgram(dist,range,psill,nugget),data = empvar, start=list(psill=130, range=65, nugget=180),trace=T) The result obtained from the nls fitting is Nonlinear regression model model: gamma ~ sph.vgram(dist, range, psill, nugget) data: empvar psill range nugget 90.7071423 342.1025007 278.9542178 residual sum-of-squares: 1140.67875 Number of iterations to convergence: 18 Achieved convergence tolerance: 9.79837651e-06 Could anyone explain why large difference in the two result? Is the R script for fitting the NLS right? I am worried for having such disparity. Thanks while looking forward to reading your suggestion, comments and advice. Moshood.
    Richard James Telford · University of Bergen
    fit.variogram is weighted by the number of observations in each distance class - see help file for details. That might explain the difference between the fit.variogram results and the nls results.
  • Natheer Alabsi added an answer:
    What GPS mapping software do you use?
    I'm looking for the best in class software solutions with which you can do the following:
    a) define a map with territorial units (e.g. district, region, country, etc.),
    b) import GPS coordinates and another associated variable (e.g. self-reported well-being),
    c) calculate the average per territorial unit of these associated variable values,
    d) colour-code the average values from min to max,
    e) export the map.
    Natheer Alabsi · The University of Tokyo
    you can try Trimble GPS Analyst extension for ArcGIS
  • Nashon Adero added an answer:
    Besides LiDAR, through which other means can you generate powerful point cloud data nowadays?
    Feature extraction
    Nashon Adero · Oakar Services Ltd
    Thanks for the answers.
  • Uttam Laisram added an answer:
    Can anyone tell me on what basis the areas of each state and country (referring to India) have been calculated and published as official figures?
    I am told that adding the area of various Survey of India Toposheets for a state does not add up to the official state area. Moreover, the satellite images after geo-referencing also tend to have inaccuracy. So while generating district-wise statistics for say, land cover and land use, and adding them up, the total land area does not tally with the official state area. How to solve this?
    Uttam Laisram · DST, Manipur
    Thank you Ana-Maria. Yes, the same projection is a must and sometimes this was overlooked. More importantly. what I really want to understand is who measured the sizes of countries and states, as found in encyclopedias and official publications, and whether the methodology followed then holds accuracy till date.
  • Richard Gloaguen added an answer:
    How can I apply reverse model to polarimetric SAR data for driving soil moisture?

About Geomatics

Geomatics is a synergism of various disciplines - Geographical Information System (GIS), computerised databases and applications, computer science, graphical processing, cartography, photogrammetry, statistics, remote sensing etc. The applications of Geomatics includes the real-world problems of management of natural and man-made environment and of the objects related to it. This would encompass the fields of natural resources management, resources planning and decision-making etc.

Topic Followers (4530) See all