Latest Contributions by EduardoMachicado

‎03-02-2020

Hi, I have been trying to model a surface using SRTM 1ArcSecond data. The Hillshade I can generate though is very "grainy"? Is this the quality I should expect from an SRTM DEM? Some of this "bumps" are clearly buildings and/or vegetation. What would be the best to clear this and produce an smoother result? I tried using Focal Statistics, but the only thing I manage is to make the dem less sharp. Can you point me out in the right direction what would be the process workflow for something like this?

‎06-25-2019

I am working on a multiyear vegetation monitoring project in Kenya and was asked to calculate the NDVI. I have processed 8 years of Landsat data but for some reason, the NDVI formula using these two rasters generates a bizarre range and very odd values. I am failing to understand what is special here, would you be able to figure it out? The zip file contains the Red Band (3) and NIR (4) bands, reflectance and sun elevation corrected. NDVI1.zip is the result I get by using the standard formula: (NIR-Red)/(NIR+Red) Let me know what you think.

‎07-04-2017

Hi, I have downloaded the following GTOPO30 dem: http://glcfapp.glcf.umd.edu:8080/esdi/ftp?id=68196 When I add it to ArcGIS I get an "Inconsistent Extent" warning. Location coordinates look strange and I can't zoom in or zoom out. What is the correct projection for this file and how do you fix this to overlay to an SHP file? Thanks for your help.

‎07-02-2017

Hi, I am trying to create a DEM for Africa from scratch using the 2000 unfinished SRTM GTopo 30 ArcSec dataset. I have downloaded four GeoTiffs containing the whole continent area, but I am finding very hard to properly clean and mosaic the 4 images together into one single file. Is there an standard workflow to make the downloaded GeoTifs ready to work in ArcMap? One of the downloaded files can be found at http://glcfapp.glcf.umd.edu:8080/esdi/ftp?id=68196 I don't understand why I am unable to run any tool on the original tiff files. I generally get a 9999 Error message. Today I have been able to export the GeoTif to a GeoDBS but after that I am stuck. The things that I would like to correct are: a) Inconsistent Extent. I imagine because the projection is "incorrect". but I am failing to understand why. Projection seems to be set to GCS_WGS84, what is incorrect here and how do I fix it? b) Ocean elevation is set to -9999. I imagine I can fix this with the Raster Calculator and the "SetNull" function. Is it worth it? c) Is there anything else I should be aware of when working with this particular set of SRTM data? I would appreciate any guidance on this. Thank you for your help.

‎06-02-2013

Thanks for your answer. I have been fiddling around with the ASTER this past days and getter better results. One of the main issues was that I wasn't really paying attention to the fact that values between both DEMs were so different which of course made me realize that ASTER was actually in feet and using a Z factor of 1 was wrong. I do not need to generate more accuracy really. It would be helpful though to know if there is a tutorial on how to filter the noise from the ASTER. The water bodies look a bit weird even when the Z factor is correct, I imagine that they need some sort of post processing. Does anyone know about any good tutorials for this (Filtering, Smoothing, etc.)?

‎05-31-2013

Hey there!. I am doing landscape archaeology in eastern Bolivia and I have been working with SRTM to get elevation data for the region. This part of the world is a bit tricky because there is really not that much change in elevation so all DEMs tend to be relatively flat but with lot of noise because of the trees. Nevertheless SRTM has worked for me really nicely, at least at the biggest scale. At this point I would like to focus a bit more in a specific part of the region and decided to use the japanese/nasa aster data. The DEM looks fantastic but I have been having a lot of troubles trying to generate a decent hillshade. I am attaching a file that compares the results of both. I have generated both using the same procedure (Project to WGS84 UTM 20S, Hillshade with Z-factor 1, since data is in MTS). You see that the results are dramatically different. Is there any other recommended procedure to generate better results with ASTER? Any help would be greatly appreciated!. [ATTACH=CONFIG]24849[/ATTACH]

‎07-03-2010

Hi there, I'm an archaeologist preparing a survey in the Bolivian Amazon. I ran into a stack of old (but in mint condition) aerial photography (from a flight around 1963 I think) that I'd like to scan an add to the geodatabase. I''ve done this before but I was wondering if anyone out there have some tips on what would be the best way to scan the pictures, any specific settings with the scanner? best formats? any other recommendations? I will appreciate any comments on experiences doing this. Thanks a lot.

‎07-02-2010

Ok, I figured it out, you need one file FOR EACH BAND literally. Thank you so much for your help, the ETM+ panchromatic band is awesome, I've been working with 3 arc second STRMs for very long, I'm super excited about this. Can anyone point me into a good resource to properly use the rest of the bands? I really want to learn how to work with this data. Thanks

‎07-02-2010

I am quite sympathetic. All the different file formats for remote sensing data can be quite a challenge. I would check if GeoTiff's are available for this scene. Historically GeoTiff was the format GLCF distributed data in. As far as I can tell here is what your header (hdr) file should look like for bands 1-5 and 7 (will need a separate hdr file for each band). Image BSQ header file nrows 6951 ncols 7871 nbands 1 nbits 8 layout bsq skipbytes 0 ulxmap 210000.000 ulymap 8505000.000 xdim 30 ydim 30 Here is the info I extracted from the metadata for the reflectance bands (1-5 & 7). nrows - PRODUCT_SAMPLES_REF = 7871 (Can't remember if this is row or col) ncols - PRODUCT_LINES_REF = 6951 (Can't remember if this is row or col) ulxmap - PRODUCT_UL_CORNER_MAPX = 210000.000 (Looks like UTM coord for zone -20) ulymap - PRODUCT_UL_CORNER_MAPY = 8505000.000 (Looks like UTM coord for zone -20) xdim - GRID_CELL_SIZE_REF = 30.000000 ydim - GRID_CELL_SIZE_REF = 30.000000 Here is where it gets tricky. The data is band-sequential so when you import bands 6H, 6L (thermal) and 8 (panchromatic) you will need to change the header info to reflect different row,column dimensions and cell resolutions. The suffix in the metadata for bands 1-5 & 7 - "REF", for 6L and 6L - "THM", and band 8 - "PAN". As soon as you get this working I would export each band into a grid and then use MAKESTACK (available in raster calculator) to make an image stack for multispectral viewing. Thank you so much for your help, I've been trying to figure this out by myself for long, since I'm right now down in the field. I created the hdr file but it doesnt seem is being read by ARCmap when I add the HDF file. Could it be because of naming convention? how do you relate a specific .hdr to the dataset? so far, the file I created is named L712320070_07020000612_HDF.hdr, same name as the L712320070_07020000612_hdf.bsq. am I missing something? Thank you again.

‎07-02-2010

Hi there, I'm an archaeologist trying to integrate Landsat ETM+ imagery to a regional survey in the Bolivian Amazon Basin. I've downloaded a file from the Global Land Cover Facility (http://glcf.umiacs.umd.edu) that came in L1G format. So far I have followed the directions given at this web page "http://glcf.umiacs.umd.edu/library/guide/fileformat.shtml", and "http://glcf.umiacs.umd.edu//library/pdf/fileguide_l1g_arcgis.pdf" but I'm having problems with step 2, creating a World File. According to the first link I should be able to find all the information needed in the metadata file, but there is SO MUCH information there that I don't know what should I copy to the hdr file and what should the the correct name of the hdr file. Without it I try to import the data, the files load but Im not able to see anything. I am attaching the metadata file to this post. Could anyone give me hand making the world file? Maybe I'm doing something wrong? can anyone post a better tutorial on how to use Landsat ETM+ files in ArcMap 9.3? Thanks a lot

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My Ideas

Latest Contributions by EduardoMachicado

Is this the best surface I can get from SRTM?

Problems calculating NDVI from Landsat

GTOPO30 correct projection

Basic GTOPO30 GeoTif workflow

Re: Hillshading

Hillshading

Old Aerial Photos

Re: Displaying Landsat ETM+

Re: Displaying Landsat ETM+

Displaying Landsat ETM+