aionyeah Posted August 31, 2011 Report Share Posted August 31, 2011 Hello pls you tell me the steps required to conduct NDVI on landsat imageries from 2000 to 2009. I am using Erdas and am new to everything. thank you just following up to the above. i want to map mosquito breeding habitats using an ndvi stratification. from literature ndvi values of 0.54 and above re associated with potential mosquito habitats. i want to see how these habitats change over the years for the period 2000 to 2009. i have chosen to use landsat instead of modis cos of the spatial resolution which is too coarse and will make me miss identifying almost all habitats. i have downloaded landsat for this period with L1T correction and also with imageries that are slc-off. i am using erdas software to achieve this huge task. where do i start from. do i need to do any further correction on the landsat imageries since they are multi temporal though they are all landsat 7 etm+ and they are L1T status? how do i go about correcting for the slc off issues? how do i derive ndvi using erdas? I saw an ndvi tool in erdas and it asks me for the imagery type and it doesn't have landsat etm+ only landsat 7 option. do they mean same imagery? I then tried to do it with the model maker but I cannot even figure it out and how to build the model. thank you Quote Link to comment Share on other sites More sharing options...
3dbu Posted August 31, 2011 Report Share Posted August 31, 2011 explain better ,really what are you try to do...make changes land analyst with NDVI, or what....explain better for so try to help; regards Quote Link to comment Share on other sites More sharing options...
sigologo Posted August 31, 2011 Report Share Posted August 31, 2011 Try with MODIS MOD13A3 Quote Link to comment Share on other sites More sharing options...
aionyeah Posted August 31, 2011 Author Report Share Posted August 31, 2011 Try with MODIS MOD13A3 i have tried to provide more explanation as per above. txs Quote Link to comment Share on other sites More sharing options...
3dbu Posted August 31, 2011 Report Share Posted August 31, 2011 big task that have to do...but is very usefull know how.... 1. have to know the process for calculate the NDVI , whats band ares inside of the calculate process: NDVI: Normalized Difference Vegetation Index: for lansat TM: for lansat 7: Just take the band 3 and band 4 and use the same formula like lansat TM. in erdas have two Model (model maker module) ther can get the right model for make NDVI analyst. With the problems of slc-off get in this forum the GAPFilling soft ( http://gisarea.com/index.php?topic=552.0 )and use it for resolve this SLC-off . this topic can hep to you for too. http://gisarea.com/index.php?topic=1476.0 . regards Quote Link to comment Share on other sites More sharing options...
aionyeah Posted August 31, 2011 Author Report Share Posted August 31, 2011 big task that have to do...but is very usefull know how.... 1. have to know the process for calculate the NDVI , whats band ares inside of the calculate process: NDVI: Normalized Difference Vegetation Index: for lansat TM: for lansat 7: Just take the band 3 and band 4 and use the same formula like lansat TM. in erdas have two Model (model maker module) ther can get the right model for make NDVI analyst. With the problems of slc-off get in this forum the GAPFilling soft ( http://gisarea.com/index.php?topic=552.0 )and use it for resolve this SLC-off . this topic can hep to you for too. http://gisarea.com/index.php?topic=1476.0 . regards Thank you for your help. For the landsat L1T do I need to do any radiometric or geometric correction? Quote Link to comment Share on other sites More sharing options...
3dbu Posted September 1, 2011 Report Share Posted September 1, 2011 http://edcsns17.cr.usgs.gov/helpdocs/landsat/product_descriptions.html hre have your answer to all your question man... good luck. regards Quote Link to comment Share on other sites More sharing options...
deepgis Posted September 4, 2011 Report Share Posted September 4, 2011 It is necessary to get the stretch value of NDVI Images between -1 to +1. For this follow the steps given below 1. Do atmospheric correction of TM images using ATCOR 3D utility. (Include the 6th A band also). 2. Remove the 6th band from the resultant image using layer stack utility. 3. Convert your resultant image iinto reflectance using LANDSAT 7 reflectance utility. 4. Use resultant image to generate NDVI images. 5. You will get the stretch between -1 to +1. The LUT value and NDVI value will be the same in all ndvi images (but histogram value will be changed). Quote Link to comment Share on other sites More sharing options...
3dbu Posted September 5, 2011 Report Share Posted September 5, 2011 It is necessary to get the stretch value of NDVI Images between -1 to +1. For this follow the steps given below 1. Do atmospheric correction of TM images using ATCOR 3D utility. (Include the 6th A band also). 2. Remove the 6th band from the resultant image using layer stack utility. 3. Convert your resultant image iinto reflectance using LANDSAT 7 reflectance utility. 4. Use resultant image to generate NDVI images. 5. You will get the stretch between -1 to +1. The LUT value and NDVI value will be the same in all ndvi images (but histogram value will be changed). would you share an tutorial with images the how to for have more clear this methods. Quote Link to comment Share on other sites More sharing options...
aionyeah Posted September 6, 2011 Author Report Share Posted September 6, 2011 thank you for all the information, this has been really useful, I will implement and come back with any other questions I have. Quote Link to comment Share on other sites More sharing options...
deepgis Posted September 10, 2011 Report Share Posted September 10, 2011 Respected 3dbu NAMASKAR I have done a very analytical study of changes in vegetative cover in my study region using the images of 1976 (TM MSS), 1990 (Landsat-5), 2005 (Landsat-7 etm) and 2010 (Landsat-7 etm) to create ndvi images. All these images were of October month. After doing lot of study I got success to get the stretch of all the ndvi images from -1 to +1. I followed the steps I mentioned in my previous post. The most important step is 3 where we have to get output reflectance image in unsigned 8 bit format (In case of Landsat-7 images). I got the same lut value and ndvi value in all the images (for example in the attribute table of all the ndvi images I got the 0.25 ndvi value at the lut value of 160). Interestingly, I didn't covert my atcor images of 1976 and 1990 into reflectance images, despite this, I got the stretch value from -1 to +1. It is my wish to share my this study in form of tutorial but I don't know how to take screen shot and edit those shots and upload to this forum. Quote Link to comment Share on other sites More sharing options...
reimari Posted October 20, 2011 Report Share Posted October 20, 2011 Why do you want to stretch the values between -1 and 1? Aren't they allready inside it? If they aren't then there is a problem with the original data (i.e. negative values). With good data set and correctly calculated NDVI you'll always get a ratio between -1 and 1 no matter what the units you put in are (DN, radiance or reflectance). Reflectance with atleast atmospheric correction should give the most reliable results. Quote Link to comment Share on other sites More sharing options...
nichess Posted February 3, 2012 Report Share Posted February 3, 2012 Thank you for the information! But step 3. I don't understand ... In the ACTOR 3D pdf the main processing steps are described as follows: [hide]http://www.satchidananda.de/img/processing-steps.png [/hide] I think that ACTOR 3D is creating a reflecting image as final product, isn't it? Best Nicoyonic Quote Link to comment Share on other sites More sharing options...
haish Posted May 7, 2012 Report Share Posted May 7, 2012 Just a little suggestion. . Do not use the slc-off imagery, even if you could make a correction and the results is visually interpretable. Quote Link to comment Share on other sites More sharing options...
3dbu Posted May 10, 2012 Report Share Posted May 10, 2012 Respected 3dbu NAMASKAR I have done a very analytical study of changes in vegetative cover in my study region using the images of 1976 (TM MSS), 1990 (Landsat-5), 2005 (Landsat-7 etm) and 2010 (Landsat-7 etm) to create ndvi images. All these images were of October month. After doing lot of study I got success to get the stretch of all the ndvi images from -1 to +1. I followed the steps I mentioned in my previous post. The most important step is 3 where we have to get output reflectance image in unsigned 8 bit format (In case of Landsat-7 images). I got the same lut value and ndvi value in all the images (for example in the attribute table of all the ndvi images I got the 0.25 ndvi value at the lut value of 160). Interestingly, I didn't covert my atcor images of 1976 and 1990 into reflectance images, despite this, I got the stretch value from -1 to +1. It is my wish to share my this study in form of tutorial but I don't know how to take screen shot and edit those shots and upload to this forum. great man good if you want to share with us all your study and result make capture with some software that make there are many if nos is possible keep each step and make a video recording your sesion use camptasia,and other ....and share it in video format for see it and learn more of your experience...regads Quote Link to comment Share on other sites More sharing options...
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