Georgeina Posted April 19, 2017 Report Share Posted April 19, 2017 Hello Colleagues, I really need help and fast too. I am carrying out a change trajectory change detection analysis looking at how much has changed over the last 25 to 30 years over a local community. My timeline for this review is between 1986 to 2012. I want to generate a NDVI time series over this area so I need at least 15 images to compute NDVI and subject it into a statistical analysis. Landsat data over this area within 1985 to 2000 is very sparse and so there is a huge data inconsistency approx. 5 -6. SPOT 1-5 has about 9 images over this area. As a beginner with these image processing software, I have the following questions: 1. Is it scientifically valid to use available SPOT 1-4 and SPOT 5 images to fuse with corresponding Landsat images of the same year in order to enhance the not too good landsat images of those years? And then build up my time series archives with the good quality Landsat images? And what is the best fusion model? Can I simply use Mosaicking in ERDAS Imagine ? 2. Or do I just carry out necessary radiometric and geometric corrections of the good Landsat and SPOT 1-4 images over the area and then build a time series with data from the two sensors? Will I be committing any breach in known principles of image processing ? 3. I sincerely look forward to your valuable inputs as I have very limited time with my work. 4. Thank you all in advance Quote Link to comment Share on other sites More sharing options...
Lurker Posted April 19, 2017 Report Share Posted April 19, 2017 I just delete your double post in different sub forum, stay tune in this topic only 1. fusing two different image? so you mean pan-sharpening? then injecting spatial information to another spatial information will make some information to lost see here for detail : http://www.mdpi.com/2220-9964/3/2/507/pdf 2. those two product have different spatial resolution, so Im afraid you will get inconsistency on the result, especially between SPOT and Landsat result Quote Link to comment Share on other sites More sharing options...
whocares1980 Posted April 19, 2017 Report Share Posted April 19, 2017 Here is my suggestion ( I am not including pre-processing or post processing methods of images, I assume you know this) 1- You set a time interval to study the NDVI based on the availability of data and your study area (the change of NDVI in desert cities is different than that in other cities). 2- Of course you gonna use Landsat, so for the missing date, you gonna use SPOT images with better spatial resolution. 3- You usually do not enhance the spatial resolution of Landsat images because these images are the majority and the errors produced of each fusion will be huge for all images. what you do is to decrease the SPOT images spatial resolution to 30m, if that makes sense?. I even do not recommend fusing the images for NDVI analysis because their radiometric values will not be retained and you gonna lose a lot of information as Lurker said. 4- Do the statistical analysis. Quote Link to comment Share on other sites More sharing options...
Arhanghelul Posted April 20, 2017 Report Share Posted April 20, 2017 (edited) Question: Where can I find and donwload free SPOT satelite images ? I have read a year ago that the SPOT1-4 archive will be free, similar to Landsat archive. What is the status for SPOT images ? Download links for SPOT ? Edited April 20, 2017 by Arhanghelul Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.