IDRISI vs. ERDAS
Posted 28 May 2006 - 12:37 PM
my office is contemplating getting a Remote Sensing software like IDRISI or ERDAS.
I just wanted to ask a general question about what (if any) are the differences in applications, ease of use, and price. Since I looked on the IDRISI site, it looks like for $us 1200, my office MAY go for it.
Another point I'd like to bring up is the Spatial Analyst extention for ARCGIS. I think it does what we're looking for, but for $1500 US, i THINK they might take that option instead.
In my RS class in school we used a ARCGIS plugin from ERDAS, I can't rememer the name for it, but it was pretty pricey, i think $3500 us. But since it was a school, i'm sure they got the discoutn.
If anyone has any good intro books on using RS software(ie LANDSATS IMAGES, IKONOS etc) that would be helpful too.
Mackay and Somps
Raster is Faster, but Vector is Corrector.
Posted 29 May 2006 - 04:42 AM
There are a few Image Processing packages on the market all designed for different types of applications. The package we use is ER Mapper 7.0. It runs for about $5000. The benefits of ERMapper is its ease of use and processing on the fly. That is, you can apply different types of image processing algorithms and you see it instantly on your screen. Packages such as Erdas will create a new file and then display. All your processing can be saved in project files called Algorithms that save all the processing steps on the image or images. You can also create Virtual dataset that basically allow you to daisy chain lots of complex image processing algorithms together. The other advantage is its compression that will allow you to compress the data upwards of 20-50:1. It uses its proprietary ecw wavelet compression format but the newer version is capable of reading/writing Jpeg 2000 format (which can be read by ArcGIS). The downside of ERMapper is its poor export formats (although ArcGrid is supported), its poor orthorectification capabilities and the difficult manner of adding new Datums and Projections. It does have alot of capabilities for using Radar data as well.
ERDAS is very good at doing data importing, adding custom projections and now Orthorectification. I have only used that side of it so I can't comment on other aspects of the program. I do know it is quite expensive (>$10000). Another package you might want to look at is ENVI. It was design for hyperspectral processing but has some newer functionality including the ability to create DEMs (I think add on module) fro ASTER data. The cost is equivalent to ERMapper. PCI is your other option, but I haven't used it in a while. For a small shop, ERMapper is probably your best bet.
Spatial Analyst is a great package but it is not an image processing package. Spatial Analyst is primarily used for Raster based modeling. I think the package you are talking about is Image Analyst which was design by ERDAS for ESRI. It has alot of good functionality that are canned. That is, I think you can only do certain tasks (Image Subtraction, Vegetation Indexs, etc).
Good text books on RS are:
"Remote Sensing of the Environment" by John Jensen
"Remote Sensing and Image Interpretation" by Lillesand & Kiefer
I don't know any good software books on using imagery.
Hope this helps.
Posted 29 May 2006 - 07:29 AM
The Jensen book is probably the best comprehensive introduction around, it is current and has great bibliographic references although it limits itself to optical remote sensing.
As for software you have a lot of options from free stuff (multispec, IPW, Ilwis, SPRING) and to very expensive PCI, ENVI and Erdas. I think that each has its strength. ENVI is very good for multispectral as Bruce indicated, it can do certain types of analysis (linear spectral mixture) out of the box very easily and is good to have around for those types of things.
I use PCI Geomatics alot for its strong ortho-rectification module and its really comprehensive set of tools. If you are only going to get one set of software you should consider PCI or ERDAS because they both have a wide set of tools. I have not used ER Mapper.
Idrisi has some very cool neural networks classifiers and change detection modules that are not available in any other software out of the box. If you have any interest in state of the art classification like neural nets or decision trees this is a good way to go and it is very affordable.
I got a license for it exclusively for those capabilities.
Another tool to consider but not on its own is eCognition. Image segmentation is going to be used more and more for extracting data from imagery and having the skills and tools to do so will be important. It is expensive software though...
Of the free software I have only used Multispec and IPW. IPW can do some really cool stuff but it is enitrely command line driven and UNIX based. It is not the most user friendly thing around but it has some very powerful image classification options such as segmentation, and neural networks classifiers.
The mosty important thing to consider is what do you want to do with it. If all you want to do is classify image from places like the GLCF, something like Idrisi or ER Mapper or even a free product like Multispec will be sufficient. If you want to work with imagery specifically acquired for your projects which will require ortho-rectification, and some of the more comprehensive analysis other packages will be preferable. Another thing to consider is ease of use, cost of training and availability of training material. In that regards I would give very good recommendations to ENVI for being extremely easy to use and learn.
There are reviews around for most of these products if you look for them (e.g. PCI Geomatics 10 review), and fairly active user communities that can help answer more detailed questions.
Posted 29 May 2006 - 08:13 AM
Posted 29 May 2006 - 11:01 AM
The new version of IDRISI, Andes, looks very impressive (haven't upgraded yet). OSSIm, for those who haven't heard about it, can be found here: OSSIM Link
And GRASS can be found here: GRASS Link. (The QGIS interface is a very handy front-end to GRASS).
Another software package along the line of eCognition is Feature Analyst extension for ArcGIS. It uses object pattern recognition as well as spectral classification techniques for extracting features. We used it to extract agricultural areas here in Saudi. Spectral classification wasn't sufficient as alot of the the areas were fallow. Agriculture here is grown mostly using pivot irrigation so Feature Analyst was able to extract the agricultural areas more accurately. As Martin said, you need to ask yourself what the package is going to be used for. I also agree that you would probably be better off getting ENVI or ERMapper.
Posted 30 May 2006 - 06:55 PM
That might have changed with the newest release, I don't know because I switched to ENVI about 1.5 years ago. It is more forgiving and has much greater capabilites. As was also mentioned in an earlier post, it appears to have been designed with hyperspectral processing in mind, however I use it for multispectral processing of Landsat and have found it can do everything I want including neural net and decision tree classification as well all the other mainstream methods. I also use it to repair SRTM data and mosaic Landsat data. ENVI has very good help and tutorials including webcasts from RSI which I found to be a good mix of theory and demonstration of what buttons to push.
If you want to classify imagery both of these packages will get the job done and I think you will get what you pay for with either software package.
Posted 30 May 2006 - 10:14 PM
Since I'm not that skilled in RS capabilities, I think the best bet is the IDRISI pack. I didnt' realize ER Mapper and Erdas were that pricey.
It doesn't look too intimidating, and I think the manager will go for it. I'm thinking we can use this puppy on some of the more high end projects we have. Maybe classifying grasses, trees, bushes, (hopefully wetlands too - mitigations purposes for the Corps:) those guys always ask the world!)
I'm hoping that my request goes well, if not, I may have to go the Open Source route.
I've' looked into OSSIM before(never got it to work). But now it seems like there are some other alternatives. I think I'm going to look into the Multispec.
Thanks a lot for the suggestions.
Mackay and Somps
Raster is Faster, but Vector is Corrector.
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