Remote Sensing

Remote Sensing

  • Mohammad Sedghi-Asl added an answer:
    What is the best way to take soil moisture and corresponding thermal infrared (TIR) measurements for the top part of a soil?

    I am carrying out a lab experiment to see the effect of dry and wet soil on Emitted Radiance. The results are anticipated to help develop an understanding of how soil moisture influences Geothermal anomaly detection in remotely sensed data. To determine the amount of moisture in a soil sample, standard gravimetric method will be followed and the ratio of water content to dry soil will be recorded in %. For the associated Spectral measurements a Fourier Transform Infrared (FT-IR) Spectrometer ( 2.5 to 16 µm ) will be used to retrieve the directional-hemispherical reflectance values and subsequently converted into emissivity using Kirchoff's law. Using emissivity and temperature the Emitted Radiance can be calculated for each soil type in dry and wet states using Planck's black body equation. Emissivity measurements are crucial for accurate land surface temperature estimation.

    However, setting-up the experiment requires some careful considerations. For example, it is challenging to keep soil sample homogeneously wet at least as long as the measurements are taken before the top part of the soil dries up. One of the suggestions is to take the spectral and soil moisture measurements quickly to have a good estimation of the soil moisture at the top layer. Since the TIR measurements are restricted only to the top few micrometers/sub millimeters of the soil surface or otherwise known as the skin level, it is essential that the soil moisture measurements correspond to the TIR measurements.

    Are there any alternative ways to do the same experiment? What other challenges can be expected?

    Mohammad Sedghi-Asl

    As I understand correctly, you want to depict SMC. You need to have soil moisture for suction or metrics. You need a Pressure Plate to measure soil moistures at different pressures (negative pressure=suction). From Field capacity moisture (pressure=-0.33 atm to PWP((permanent wilting point)=-15 atm). You need at least 10 points to suitable distribution along this suction ranges.   

  • Hojjat Seyyedi added an answer:
    How to download spatially subsetted long term time series of precipitation data?

    I need to download spatially subsetted long term time series of precipitation data. It can be any type of precipitation data including TRMM, PERSIANN, GLDAS and NLDAS. As you know all NASA and NOAA supported websites are limited to maximum length of 6 months (if you want 1hr or 3hr temp resolution) due to the volume of data and etc. I cant really download the high temp resolution data for 10 years or 20 years through their website unless I resubmit the same request for many times. Any type of information or code or website that you can share with me to solve this issue would be greatly appreciated.

    Hojjat Seyyedi

     Thank you Vitor.

    The maximum number of items that we can download through mirador is 30000. Plus the files are not really subsetted to the area of interest. They are just simply global data which needs some sorts of post processing. 

  • Alireza Arofteh added an answer:
    How do I reduce speckle in image of SAR with sub looking?

    i have image of ocean and it have more speckle how can i reduce it?

    Alireza Arofteh

    thanks guide

  • David Fischel added an answer:
    How can I predict missing pixels changes in remote sensed environment?

    wide and variety fields in remote sensing, my current research is a part of CSIRO that work on finding missing pixels in sights that may contain changes in the environment. I use C++ with Linux. The basic of this research is based on the geo_statistical variables to find out the changes in each pixel and combine them through a linear relation via time series.

    David Fischel

    This was a problem in some early instrumentaion. Since a primary data acquisition organization does not have the time to research earlier data, the method has always been an average of adjacent pixels. If you have the time and resources, a visual presentation is a more rigorous approach. You need to do this if there is any chance that the missing pixel is actually on a road, not the adjacent field (whatever may be there) or similar drastic reflectivity change. Some experience with the data then could lead to an automatic choice of algorithms. An early Indian satellite lost data in this way. Their solution used data from other spectral bands to "predict" what ought to be in the missing pixel. You can use older data to generate a predictor model. The underlying rationale for this method is that a multispectrral data set normally has redundancy between the spectral bands. If, alternatively, you are missing a panchromatic pixel, you can use the ,olh pan data to predict, as suggested. Or, use the multispectral data to prdict the pan.  Good luck!

  • Girish Babu M C asked a question:
    How can we estimate prediction- yield of rice/sugarcane in data mining for remote sensing dataset-images at national/state level ?


  • Seyed Amir Naghibi added an answer:
    How can we determine the source and the path of the oil spill using satellite images?

    Dear Experts.

    I need to know is it possible to do the mentioned work. If yes, what satellite/images do I need. Is there any methodology or reference which could help me?


    Seyed Amir Naghibi

    Dear Tamara and Chunxiang.

    Thank you so much.

  • Armin Doerry added an answer:
    What is the difference between missile-borne and air-borne SAR images?
    I am planning to register missile borne SAR images and optical pictures and want to know the differences between missle-borne and air-borne SAR images
    Armin Doerry

    SAR cares about imaging geometry, and not the vehicle/platform on which the radar is located...  Once you have an image, you can't tell what the vehicle was from which the data was collected...  So, no difference...

  • Soodabeh Amirinezhad added an answer:
    How do directions of GLCM work for calculating texture on the image?

    Hello colleagues, 

    I am using GLCM to extract texture-based information from the image of a forest. I want to use different window sizes of 3*3, 5*5 and 7*7 for each band. But I have a question about the purpose of using different directions such as 0,45,90 and 135 degree. I do not know how they work and what are their functionality? I would appreciate if someone explain or introduce any source for reading.

    Thanks in advance.

    Soodabeh Amirinezhad

    Thank you Dr. Chavez and Dr. Wulder for this informative response. I really appreciate. I hope reading can help me to find out more. 

  • Bart Kowalski added an answer:
    How feasible is it to do Evapo-transpiration Mapping using Radiative transfer model and remotely sensed data?

    Radiative transfer model brings very complex algorithm to solve the model.

  • Karolina Pantazatou added an answer:
    How do I compare distance-to-water values computed at two different geographic levels?


    It would be great to get your feedback on the following question.

    My data set contains counties and their respective municipalities. I have computed the minimum distance to fresh water (lake or stream or river, etc) for all municipalities in a municipal layer, as the shortest Euclidean distance between the centroid of the municipality polygon and the border of a lake (polygon), stream (poly-line) or river (polyline). I have done the same for every county in a county layer, by calculating the shortest distance from every county's polygon centroid to fresh water (lake, stream, river, etc.).  

    Now I want to statistically compare the results from both layers to estimate how much the distance-to-water results differ from one layer to another. For example, what is the average difference in meters when calculating distance-to-water on a county-level rather than on a municipality-level? How much can the results differ depending on which layer is used? Does anyone know which statistical method is most suitable to solve this problem?

    Thank you in advance.

    Karolina Pantazatou

    Thank you all for your answers!

    The study was a mortality study, and the reason we studied distance to water at different geographic levels had to do with the fact that historical demographic data wasn't always available for the whole study area at the same level. Therefore, we tested if and how much results might have varied, depending on at which geographic level the calculation were performed at. The layers were different divisions of property units and something that today might have been regarded as municipalities (parishes). This fact together with the notion that we studied rural communities of the past were the reason why the centroid or the border of property units were used to estimate distance from various "high risk for getting an infection" areas. Since property units and their derivatives varied in size and shape and parishes also, I agree that Alessandro's approach would be the best one to implement. Regarding the statistical analysis of the multi-level results Josep's suggestion is very good!

    I thank you all for your valuable insights!

    best regards,


  • Michael Londe added an answer:
    How do I correct an RTK survey using precise point positioning?

    I have conducted a survey of ground control points with a Trimble RTK system relative to a base station at an unknown location. I need to correct the base station position using the Natural Resources Canada CSRS-PPP application (I am trying to compare to another dataset which has used this same correction). The output of the CSRS-PPP is a .csv file with the corrected base station position for each time stamp during the survey. I don't know how to integrate that with the raw rover and base station files from the survey.

    Michael Londe

    Very good. This is one of my primary programs. If you need assistance we can make arrangements off-line for you to contact me.. One thing to watch for when seeding points in TBC is that it is useful to disable the base global coordinates prior to recalculation of all points.

  • Olivier Hagolle added an answer:
    How can I differentiate vegetation type using remote sensing?

    how to differentiate  vegetation using remote sensing?

    Olivier Hagolle

    There are other ways to distinguish several vegetation types than multiplying the number of bands as for hyperspectral data You may use the time dimension, as the different vegetation types may have different onset and senescence dates. For instance, here in Europe, we have winter and summer crops, and some of them have different crop cycle lengths, of different flowering dates.

    To do that, you may try LANDSAT data, Sentinel-2 data (not yet available, but soon), or the data from the SPOT (Take5) experiments.

    On my lab's blog, you may see an example obtained with LANDSAT using supervised classification based on time series of LANDSAT images acquired along the year  :

    + 3 more attachments

  • James Varghese added an answer:
    In extraction of soil moisture map from SMAP, is it necessary to have terrestrial measured soil moisture control data?

    In extraction of soil moisture map from SMAP, is it necessary to have terrestrial measured soil moisture control data? If the answer is positive, how can I use some point SM data to control the coarse scale SMAP data?

    In lack of the measured SM data, is it possible to use SMAP for extraction of SM data?

    Many thanks!

    James Varghese

    Thanks Dr. Luca for sharing the links. Appreciate it.

  • Armin Doerry added an answer:
    Detection of trucks and vehicles with SAR data?
    Is it possible to detect passenger vehicles and trucks with standard Single Look Complex (SLC) SAR data? By standard I mean:
    9.0 x 13m slant range resolution
    7.7m Nominal azimuth resolution
    11.8 x 5.1m Pixel Spacing
    1 equivalent No. of independent looks
    -29+-2 dB noise equivalent sigma 0
    < 1dB radiometric error
    (Standard SLC from Radarsat-2)
    Armin Doerry

    The question did not specify, so I am presuming a stationary vehicle...  The resolution given suggests that most vehicles will be a dot or very small blob in a SAR image...  RadarSat is C-band, so typical vehicle might average +5 dBsm RCS or so, so would be detectable...  Then you have to decide if your dot is a vehicle or not, which is a different question...  and very difficult without additional knowledge...

  • Prasad Daggupati added an answer:
    Can different durations and different periods of climate station data be used in a SWAT model?

    I am working on impact of climate change and land use, land cover change on sediment yield in Rawal watershed, Islamabad, Pakistan. I have total 5 stations, 2 inside and 3 outside of watershed. For one station which is inside watershed i have only rainfall from 1975 2014. For the second station which is also inside of watershed i have rainfall and Temperature (max and min) only from 1991 to 2010. For third station which is outside, i have relative humidity, Rainfall, temperature (max and min) from 1980 to 2014 and wind speed from 2006 to 2014. For fourth station which is out side, i have relative humidity from 1998 to 2014, Rainfall from 1987 to 2014, temperature (max and min) from 1990 to 2014 and wind speed from 1998 to 2014. For fifth station i have data from 2005 to 2009 only. My intention is to used maximum of this data. How can i utilize maximum of this data?

    Prasad Daggupati

    You can create a weather generator using the observed data from different time periods and develop a weather dataset with missing data with -99 so that the weather generator will replace the missing data. 

  • Solomon Njoroge Njogu added an answer:
    What are the different sites for downloading best resolution (below 20 m) for free remote sensing imagery?

    I am looking for satellite image used for academic purposes

    Solomon Njoroge Njogu

    I also found some useful references attached link.

  • Kenneth M Towe added an answer:
    Will recent warming hiatus with respect to mean temperature continue or not?

    2014 became the warmest year on record, without a strong El Niño. The so-called global warming hiatus (1998-2012) are widely concerned. In the following decade, global mean temperature warming will continue to slow down, or will rise much more rapidly than in the "slowdown" period? What are main physical causes responsible for inter-decadal changes of mean temperature?

  • Stefan Auer added an answer:
    SAR simulator RaySAR with open access - which aspects would be of main interest?

    I'm planning to open the access to RaySAR, a SAR simulator I have developed within my TUM / DLR-group. Key features, applications and the scientific framework of the simulator are summarized in the attached PDF "RaySAR_properties".

    Access to RaySAR would be devoted to the support of starters in science during their studies (as it did in my work) but also to experienced scientists lacking in 2D or 3D SAR image simulation tools so far. 

    As a first step along the road, I would like to collect feedback from scientists who would expect to benefit from using RaySAR.

    Hence, my question is:

    How may RaySAR support your scientific work?

    (The answer may be given here, fostering the discussion of RaySAR, but also via e-mail to

    Stefan Auer

    Yes, I will. It will just take some time to wrap everything to a package 😊.

  • Armando Jesús De la Colina Rodríguez added an answer:
    Is it possible to use remote sensing to determine the levels of intensity of use of land?

    Can identify the intensity of agricultural production systems and levels of fertilization, mechanization and other applied through remote sensing?

    Armando Jesús De la Colina Rodríguez

    Norman: I think your answer is very clear, when I ask the question I referred to the intensity of agricultural production units in relation to the use of agrochemicals, mechanization, intensity of labor, irrigation at a municipal level to get it's cartography 1:25 000 or smaller scale. His remarks are illustrative of that is required to be clear the purpose and scope of the investigation. Thanks for your reply. Best regards, Dr. de la Colina.

  • Oula Seitsonen added an answer:
    How can I download satellite images that have resolution of 30m ?

    How can I download satellite images that have resolution of 30m ? with remote sensing, counter mapping and spatial analysis?

    Oula Seitsonen

    Depends also where you are in the world and what you want from the data. For instance 30 m DEMs are available from Aster (

  • Minu Punathil added an answer:
    Can anyone tell me which band is used for adg443 in a L2 MODISA IOP file?

    Can anyone tell me which band is used for adg443 in a L2 MODISA IOP file? While plotting images in ENVI software band number is asked; please tell me which band corresponds to adg443 in the level 2 file of MODIS-A IOP. Also, which band corresponds to Chla in OC  file of MODIS-A at L2 level.

    Minu Punathil

    Thank you Mr. Javier for your information. I used SeaDAS to reproject the data and I used reprojected data in ENVI for band math calculation. 

  • Petteri Muukkonen added an answer:
    Remote sensing data or images vs remotely sensed data or images. Are they both OK?

    I have used in the past both "remote sensing" and "remotely sensed" as qualifiers to refer to data acquired by airborne or spaceborne sensors. However,  I feel increasingly uneasy about "remotely sensed", because I find it convoluted and even a bit pedantic. I would like to convince co-authors to give up using "remotely sensed", and I offer two arguments:

    1. A digital picture of a lake taken  from the top of a mountain was indeed remotely sensed, but it's clearly not what we would understand as a remote sensing image.
    2. 'remotely sensed' is a secondary jargon derived from the primary jargon 'remote sensing'. Why should we use yet one more jargon when the original one can also work as an adjective?

    Can you come up with any other supporting argument, or if you prefer 'remotely sensed', can you come up with a counterargument?

    Petteri Muukkonen

    Both terms might be OK, but the term "remote sensing" is nowadays more common.

  • Emil A. Cherrington added an answer:
    Which SAR data are freely available?

    In a soil moisture study, I need to have the spatial distribution of soil moisture in high resolution, to evaluate its relationship with topographic factors.

    Emil A. Cherrington

    In follow-up to Joao's answer, you can access archived imagery from ALOS PALSAR from the following portal of the Alaska Satellite Facility: All you need to access the data is to have / create a NASA EOSDIS account and click "I agree" on the terms and conditions for the data. You will have access to the archive of PALSAR data from ~2006-2011.

  • Olutoyin A Fashae added an answer:
    What are the various indices for validating different types of DEMs for its accuracy and precision?

    What are the various indices for validating different types of DEMs for its accuracy and precision?

    Olutoyin A Fashae

    Thank you all for the information.

  • Taqiy Eddine Boukelia added an answer:
    How to calculate the empirical coefficients A, B, & C in the Bristow–Campbell model for estimating the Solar Radiation?

    Good day, can anyone please share the equations and the methodology which is employed for calculating the empirical coefficients for the Bristow-Campbell model? 

    Taqiy Eddine Boukelia

    Dear Muhammad Munir;

    The answers of your specific questions as:

    1. These coefficients are dependent on the site of where they calculated, for example: if you calculate them in Algeria, and apply them in UAE, the models with these coefficients will give you lower performances than in Algeria.

    2. Not always, just in very specific cases.

    3.This depend on the correlation used, in some cases it is the first, and in others it is the second. Therefore you need to check the equation.

    I hope this can help

  • Ayad Mohammed Fadhil added an answer:
    How can I get the soil moisture products freely online?
    Where can I get the soil moisture products feely online? I'v been confused by the question for a long time. It will be very kind of you who can provide me some useful information about soil moisture data derived from remote sensing .
    Ayad Mohammed Fadhil

    TCW, NDWI, and NDMI of Landsat are useful indices.

  • Li Linyuan added an answer:
    How could I inquiry suomi-NPP VIIRS overpass time? By a overpass predictor?

    I want to conduct Ground synchronization of VIIRS. unfortunatelly,I don't know how to acquire its overpass. Please help me .



    Li Linyuan

    Dear Mr.James

    This link contains other satellite orbit tracks at same time. Thanks a lot.

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