Remote Sensing

Remote Sensing

  • François-Nicolas Robinne added an answer:
    Using remote sensing tool, what is the simplest method to use for studying the forest fire risk in a mediterranean region?

    Regardless of the form or method used, should we take consider all biotic and abiotic factors of the physical environment or only the climat indicator (IC) and topography indicator (ITP) ?

    Thank you for answering my question.

    François-Nicolas Robinne · University of Alberta

    Allessandro is right, niche modelling using the maximum of entropy approach has proven its usefulness. There are several software which implement it, like MAXENT or ModEco.

    This paper might be of some interest as well: "Spatial variability in wildfire probability across the western United States", Parisien & al

  • AGILAN V added an answer:
    Can anyone send me a link for a detailed LULC and shape file of Mumbai?

    I need the detailed LULC and shape file of Mumbai. Can anyone help me?

    AGILAN V · National Institute of Technology, Warangal

    https://lta.cr.usgs.gov/LULC

  • Alexandre Castagna added an answer:
    Can anyone help me to use gdalwarp to project TOMS L2 swath data using Geolocation Arrays?

    Dears,

    I'm trying to project TOMS L2 Swath data that is stored in HDF5 format. Geolocation data of latitude and longitude are stored as rasters data sets. I learned that gdalwarp can be used with the option -geoloc that forces the use of Geolocation arrays, that are more appropriate than using Ground Control Ponits (GCPs) when available (https://trac.osgeo.org/gdal/wiki/rfc4_geolocate). I tried to use gdalwarp directly on the data set with this option, but it gave no result.

    In a forum, I learned that a workaround was needed with Virtual Raster format (vrt), here: http://gis.stackexchange.com/questions/103116/map-project-a-raster-having-separate-latitude-and-longitude-raster-bands. But in trying to follow the example, my gdalwarp states that the vrt file "is not recognised as a supported file format", although my gdal has the VRT listed in the list of supported formats.

    The file I'm experimenting with is the TOMS/EP first orbit for 01/01/2001, available from MIRADOR: http://acdisc.gsfc.nasa.gov/data/s4pa/Earth_Probe_TOMS_Level2/TOMSEPL2/2001/01/TOMS-Earth-Probe_L2-TOMSEPL2_2001m0101t2357-o24157_v001-2004m0424t164428.he5

    Can anyone give me a hand? Thank you

    Alexandre Castagna · University of São Paulo

    Thank you Sebastian,

    I didn't knew about BEAM; it will be interesting to explore its functionalities.

    Actually I will need to set up a workflow to work with several files. Nevertheless, I could finally perform the transformation with GDAL. The example VRT structure on the link above was wrong, that is why gdalwarp did not recognized the VRT format. If you are interested in an option with GDAL, I'm attaching the correct VRT structures to use for this procedure, with data for projection of the test file above (they can be edited as a text file).

    With all files (includinhg the HDF5) on the same folder, the gdal command line would be:

    gdalwarp -geoloc -r cubicspline -s_srs "epsg:4326" -t_srs "+proj=longlat +ellps=WGS84 +datum=WGS84 +no_defs" -tr 1 1.25 TOMS-Earth-Probe_L2-TOMSEPL2_2000m1231t2303-o24142_v001-2004m0424t164259_1.vrt test.tif

    The output resolution of 1ºx1.25º is to mach the commom TOMS L3 data.

    Best regards,

  • Adane Birhanu Gedif added an answer:
    Is it possible to convert the pixel value of a satellite image into meters?

    I would like to know different methods which are possible to convert the pixel value of satellite image into meters. Like to know is this possible. 

    Adane Birhanu Gedif · Bahir Dar University

    I do not think that there is a method which can convert reflectance values to meters. The spectral values are unitless and describes how the given detectable object react with the EMR. By the way why you want to change it to meters. Since meter is unit of length measurement, the reflectance values, as far as my knowledge is concerned, will not help to measure distance.

  • Maria Kozlova added an answer:
    How do I perform an image difference between TM and OLI vegetation index layers?

    I'm currently trying to find the change in value between two dates for a couple vegetation indices generated from two different types of Landsat data. The first image is a TM image from 2011 and the second is a 2013 Landsat 8 OLI image. Both images are georegistered and converted to atmospherically corrected TOA values. While doing some preliminary investigating, I found that the values for unchanged landscape features are significantly different between dates. I'm wondering if this is a result of the difference in radiometric resolution between the sensors (8bit vs 12bit). The Landsat 8 values appear to be lower in a number of areas compared to the TM. Whats should I do to accurately difference the images?

    Maria Kozlova · State Oceanographic Institute

    I' like to add one more comment from different point of view.
    The area of your study is also very important. After you complete image processing referred above, you should take into account any natural factors that can influence NDVI values (vegetation activity) 'in situ' such as hydrological factors and atmospheric precipitation, soil and air temperatures aroung image acquisition dates and so on.
    There are many area types that can change significantly from year to year. And so in some cases you cannot expect similar NDVI values even at similar dates in various years. And it's always better to analyze more than 2 images if possible

  • Jose Gomez Castaño added an answer:
    Where can I find high resolution images of Mars surface for educational purposes?

    I would like to use DEM of Mars surface for GIS spatial analysis classes.

    Jose Gomez Castaño · Administrator of Railway Infrastructures (ADIF)

    Hi:

    For educational purpopses perhaps you can find usefull "Map a planet" WMS services [1], and "Planetary Open Geospatial Initiative" [2]

    [1] http://www.mapaplanet.org/explorer/help/wmsUserDoc.html

    [2] http://webgis.wr.usgs.gov/ogc/index.htm

    Kind regards

  • Jianjun Wang added an answer:
    Tetracam ADC Lite camera (3.2mp, NIR-R-G) and a modified camera (16.0mp, NIR-R-G), which one is better for UAV based and/or ground based aplications?

    Any experience on this issue?

    Jianjun Wang · University of New Brunswick

    Thank you, Ralf!

  • Behrouz Ahmadi-Nedushan added an answer:
    For dams, what method is used for doing evaluation of concrete distress?

    Should we have to do continuous monitoring using remote sensors as we do the same for the bridges?

    Behrouz Ahmadi-Nedushan · University of Yazd

    Dam safety systems are systems monitoring the state of dams used for hydropower or other purposes. Emergency warnings can be issued at various degrees of automation. There are instruments to measure stress strain, with of cracks, pressures, etc
    The monitoring system may include the use of differential GPS and SAR remote sensing to monitor the risks imposed by landslides and subsidence. For large dams seismographs are used to detect reservoir-induced seismicity that could threaten the stability of the dam.

    A very good reference is:
    Guidelines for Instrumentation and Measurements for Monitoring Dam Performance for Instrumentation and Measurements for Monitoring Dam Performance
    By Task Committee on Instrumentation and Monitoring Dam Performance

    You may also want to look at attached report from United States Society on Dams.

  • Thierry Ranchin added an answer:
    Does anyone know sunshine hours data for Globe?

    Hey everyone! I would like to use monthly or daily sunshine hour or any related product for estimating water balance on large scale for year 1979 to 2012. I came across ERA Interim data sets but that is forecast data. I need analyzed data. I am focused to Indian region.

    Thierry Ranchin · ParisTech

    Dear Ara,

    you can use a free web service for www.soda-is.com

    http://www.soda-is.com/eng/services/astronomy_free_eng.php#a1

  • Satya PRAKASH Maurya added an answer:
    By using remote sensing satellite, is there any website that give us the amount of ground water in specific region in the world?

    I would like to estimate the ground water for specific region. Is there any website that can give me this estimation by using remote sensing via satellite?  

    Satya PRAKASH Maurya · Indian Institute of Technology (Banaras Hindu University) Varanasi

    As per my best knowledge Remote sensing directly can't help to estimate amount of ground water

  • Mengmeng Yang asked a question:
    Is there any software to process airborne SAR data?

    I want to gain DOM based on the data of  airborne SAR data and DEM

  • Charles A S Hall added an answer:
    Is there any negative effect in applying PCA on NDVI from two years for species distribution modeling?

    Does it have any negative effect on prediction for modeling plant species distribution, if we applied PCA on NDVI from two years (MODIS - MOD13Q1 - Resolution 250 m - 16-day)? Since some people say, if we consider winter's NDVI, it could reduce the Mean value of NDVI for a year and it can affect your prediction for modeling species distribution. I've used Maxent and GARP to model an endangered plant species.

    Charles A S Hall · College of Environmental Science and Forestry , The State University of New York

    Nothing like good ground truth form a skilled botanist.....both unto itself and to calibrate what ever you are doing.    Also its good to revisit the Clements-Gleason debate, and Whitaker's empirical support in Smokey Mtns for Gleason's individualistic concept.

  • Cristina Radnea added an answer:
    What recent work has been done on using NDVI to predict the N response of maize in temperate climates?

    We consult with dairy farms in Northeast US, and, here as elsewhere, too much N is often applied so that yields will not suffer from lack of available N. We use the pre-sidedress nitrogen tests to assess soil N supply at V4 - V6, and also the corn stalk nitrate test at harvest to assess whether maize had been supplied with sufficient N. We are looking for practical tests to use to advise our farmer clients.

    Cristina Radnea · National Research and Development Institute for Soil Science, Agrochemistry and Environmental Protection

    You may try, for example, to see the results of Yuxin Miao et al.,  published also here, in RG. He worked on N management for maize, in US and China, using ground, aerial and spatial RS.

    Dr.  Miao et al. compared many vegetation indices. You may figure out which ones perform reasonably well for practice, then see which instruments measure reflectance in the bands used by those indices.

  • Prajjwal Panday added an answer:
    Does anyone know a reliable gridded database of rainfall for Africa?

    I know there are some global database that include rainfall. But I would like something more specific for Africa at a spatial resolution around 0.25 degrees, and daily frequency for the last decade. Something equivalent to the European ECA&D would be great. Does it exist for Africa? Thanks.

    Prajjwal Panday · Woods Hole Research Center

    Victor

    CHIRP dataset is good for this region too.

    http://chg.geog.ucsb.edu/data/chirps/

    Best,

    Prajjwal

  • Egidijus Zer added an answer:
    Are there any available airborne LiDAR data in south Ottawa region, or Eastern Ontario ?

    In order to map the habitat of a bird species, using the understory layer of forest fragments, I thought that airborne LiDAR data (point clouds) would represent a promising tool. The issue is that the forest fragments (woodlots) in question are located in private lands, in south Ottawa. Is there anyone aware of airborne LiDAR data in Eastern Ontario or further, or an alternative option ?

    Thanks a lot.

    Egidijus Zer · World Star Tech

    Try contact companies who are in this business, and ministries. Maybe they had projects and be willing to share data. Otherwise write a grant to get $$$.

  • Fernando Allende Álvarez added an answer:
    Does anyone have any experience with snow cover using remote sensing techniques?

    I need to determine snow line effects on river flows?

    Fernando Allende Álvarez · Universidad Autónoma de Madrid

    Behrooz - you might wish to see EHRIN Program and methods used to estimate snow cover.

    http://www.magrama.gob.es/en/agua/temas/evaluacion-de-los-recursos-hidricos/erhin/datos-interes/

  • Fábio Marcelo Breunig added an answer:
    Are MODIS C5 Vegetation Index products corrected for topographic shadows?

    Obviously MOIDS VI products are corrected (to some extents) for cloud shadows. But how about topographic shadows? If yes, any information on DEM and methodology used for corrections?

    If no, to what extent do you think VIs (particularly NDVI) in C5 are affected by topography and illumination/viewing geometry? As far as the general appearance of the vegetation cover is concerned, my focus is not on "trees", but mostly on grass, shrubs, and subshrubs. Can I also have some suggestions from your own experiences with correcting topographic, viewing/illumination effects on NDVI?

    Fábio Marcelo Breunig · Universidade Federal de Santa Maria

    Dear

    The tpographic shadows are not addressed, as well directional effects.

  • Hayder Dibs added an answer:
    What is the best quadcopter system for wetlands mapping?

    There are many drone systems available for wetland remote sensing, but quadcopters seem to be most effective. What are the costs of using a mid-sized quadcopter?

    Hayder Dibs · Putra University, Malaysia

    my advise if you go through fix-wings will be better and faster

  • Robin Campion added an answer:
    How to retrieve volcanic SO2 from ASTER TIR?

    I want to analyze the amount of SO2 emitted from volcanic activity. I will use ASTER TIR because they provide multispectral TIR data. I read some journal that give method about that such as Campion et al 2010. But, I don't know how to do it.

    Robin Campion · Universidad Nacional Autónoma de México

    In general, volcanic CO2 and H2O are extremely dificult to measure from space, because they are already abundant in the atmosphere. H2S is also very difficult to measure from satellites (only using high-spectral resolution sensors, in large eruption clouds at high altitude). None of these gases can be measured with ASTER. What you could do is mapping the temperature anomalies and take that as a proxy for water vapor emission (with some fieldwork to quantify water vapour emission from fumarollic area, and establish the correlation with the heat output measured from space). But this may be a bit large for  a master thesis

  • Virginia Garcia-Millan added an answer:
    What are the best remote sensing techniques for mapping submerged aquatic vegetation in estuaries and river mouths?

    Can eelgrass colonies be detected from satellite altitudes?

    Virginia Garcia-Millan · EFTAS Fernerkundung Technologietransfer GmbH

    In order to study vegetation, optical sensors might be the most appropriate for you. However, as Chavez and Mahmud said, the transparency of the water you are observing is a limiting point for your study. Turbidity might mask what you are trying to see.

    If the water under study allows you to see the vegetation underneath, I recommend you 2 types of sensors: if you need to study any plant function (i.e. chlorophyll content, NPP, pigment concentration, species diversity, etc.), I better recommend you a hyperspectral sensor. If you only need to know the distribution of the vegetation communities, maybe it is enough with aerial CIR photos.

    Another key question is the resolution you need. If you don't need very high resolution, you might also use sensors of mid-spatial resolution, such as Landsat, which can be downloaded for free.

    It is always a trade-off between sensor features and price. If you provide more details on your research maybe we can better assess you.

    Good luck!

    virginia

  • Jahangir Pachkam added an answer:
    How can we calculate the correlation length from images?

    I would like to calculate the correlation length using radar image. Can you tell me what the easiest procedure to calculate the correlation length of the radar images is?

    Jahangir Pachkam · Arak University

    Hello, dear friend to visit the site now

    http://www.mathworks.com/matlabcentral/newsreader/view_thread/330987

    Good Luck

  • Mozhgan Ahmadi added an answer:
    What are the current issues in change detection techniques/approaches using remotely sensed images?
    see above
    Mozhgan Ahmadi · Islamic Azad University Khorasgan (Isfahan) Branch

    Dear Phan Thanh,

    You can use SLEUTH Land Use Change Model, Geomod and Markov model for land use/cover change modelling.

  • What is the best method for detecting and mapping clusters of small plastic particles in the upper layers of the ocean?

    Would any remote sensing techniques be able to map such clusters over large ocean surface regions?

    Sarraju Srinivasa Raja Shekhar · National Remote Sensing Centre

    A genuine answer for this as on date is "NO. Not Possible". Theoretical  "Yes" just to prove a case would be talking about very high resolution, microwave imaging etc.

    Works on Oil Spills are abundant and this was possible, not only by wavelengths employed, but due their spatially large area coverage / presence. If we talk about a cluster which is around 100 Sq.mt or above, visible on the surface, some insights can be worked out with RS techniques. 

  • Pat S. Chavez, Jr. added an answer:
    Comparing images acquired by different satellites?
    I am doing land use change detection based on landsat 5, 7 and 8 images. At the pre-processing step I have done radiometric calibration and also used dark-object subtraction technique for all scenes. The changes of the three time points based on landsat 7 offer reasonable trend as desired (forest decline). But the result of the landsat 8 image shows a sudden increase of forest area, whereas the results of landsat 5 show the minimum amount of forest area. I do not know what is wrong! Should I have considered something special when comparing images from these different satellites?
    Pat S. Chavez, Jr. · Northern Arizona University (retired USGS)

    Some good suggestions have been given by Olena, plus what you have done was a good start.  One possible issue that could explain some of what you are seeing with Landsat 8 vs 5 and 7 is that the radiometric resolution (DN dynamic range) is 11-bits vs 8-bits.  Make sure that the images are not only radiometrically corrected, but also transformed into the same dynamic range scale (e.g., if the forested vegetation have a spectral surface reflectance of say 6% that this is represented by the same DN value in the corrected form of ALL the images).

    Pat

  • Maxim Chernetskiy added an answer:
    Why is MISR retrieve better AOD than MODIS in reference ground measurements?

    I am working on MISR and MODIS Level-2 data, compare these two dataset with ground measurements: I found better correlation with MISR than MODIS, and MODIS also over estimate MISR . I also found in literature MISR AOD is better than MODIS because it use the multiangle (9 angles) at the time of image acquisition.Here my question is that how does multi-angle  increase the accuracy of MISR?

    Maxim Chernetskiy · Friedrich-Schiller-University Jena

    The answer of Michel is brilliant!

  • Raul R. Cordero added an answer:
    What would be the best technique for calibrating a UVER sensor (UVS-E-T) using a UV-B sensor (Solar Light 501 or similar)?

    I need to calibrate a UVS-E-T (calibrated in 2012) and I´ve available only a SL 501 radiometer. 

    Raul R. Cordero · University of Santiago, Chile

    It seems to be not possible due to the the fact that both instruments may have different spectral responses. You may need a spectroradiometer as reference for calibrating both instruments. 

  • Eko Susilo added an answer:
    How can I measure eddy from SAR?

    I'a still newbie in SAR processing

    Does anybody have experience to measure the eddy (size, evolution, ect) using SAR data? I have several SAR image data, may be samoboday want to share your experiences to me...

    Happy new year for all of fiends and collage..

    Eko Susilo · Ministry of Marine Affairs and Fisheries

    Hi Hayder, 

    what do you mean about decision rule? do you have relevant litterateurs about that?

  • Does anyone know of a global database of air/surface temperature and rainfall with a finer resolution than NCEP/NCAR reanalysis?

    I know the European Climate and Assessment & Dataset at 0.22 degree (http://eca.knmi.nl/download/ensembles/download.php#datafiles). I am interested in something at this resolution of better for the whole world, or other databases for other continents which I could use together with the European one.

    Thanks.

    Victor Francisco Rodriguez-Galiano · University of Southampton

    Kristopher, thanks for your answer. Could you please provide a link for the data, and additional information such as temporal coverage and temporal frequency.

    Thanks

  • João Paulo Pereira added an answer:
    Pattern recognition algorithms by combining GIS line data, high resolution aerial photography and remote sensed images?
    I am attempting to combine GIS line data, high resolution aerial photography and remote sensed images (thermal and possibly radar) to develop training sets or algorithms for pattern recognition. Is it possible to combine all three in the same process/programme/coding?
    João Paulo Pereira · University of Freiburg

    I agree with Marian Koch. I'm developing my PhD Thesis here in Germany using scikit for pattern recognition in images derived from LiDAR data. Both Python and Scikit are both very good ways to do what you want. Plus, you don't have to create the whole programming, much of the stuff is already written. All you have to do is to apply in your data. In youtube you can find a lot of videos and tutorials explaining the basics of Scikit-leaning.

  • Hanqiu Xu added an answer:
    How do I observe a low Correlation of suspended solids concentrations with near infrared band?

    I am using a combined dataset of Landsat TM, ETM+ and Chinese HJ-1 A/B CCD sensors images coincident with the in situ measured Suspended Solid Concentrations (SSC) for my study area Hong Kong. All these sensors are similar in spatial resolution (30 m), bands designations and data bit levels (8 bit). I have used the four bands Blue, Green, Red and NIR to find their correlation with coincident SSC.

    I am observing a low correlation between NIR and SSC, while in literature a higher correlation has been reported.

    Can someone explain why there is low correlation between NIR band and SSC for my study area? 

    Can this be attributed to the specific grain size and particle size distribution of the suspended solids found in this region?

    Any comments will be appreciated.

    Thanks

    Hanqiu Xu · Fuzhou University

    SSC usually has a high correlation with Red band rather than NIR band. You might try Red band to see what happen. A low correlation could also be caused by the mismatch between image pixel and in-situ sample point.

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