Hi Berry: Thanks for your clarifying explanation. I have a long time experience working with images in Caliper products (since DOS versions) and you are totally correct regarding the poor quality of JPG. But I would like to take the opportunity of your message, to ask for help please. Since the appearance of MrSID images in Maptitude (I believe version 4.5), we have been using this facility because as you mentioned the quality and specially the size of such type of images made them the best choice, but recently I have found a problem that I do not know how to solve:
I have downloaded several satellite images of Brazil from John C. Stennis Space Center in NASA (https://zulu.ssc.nasa.gov/mrsid/). These images came in MrSID georeferenced format. I managed to display them in the correct position with Maptitude version 4.7 (it is necessary to subtract some amount from the SDW file, to made them show in the correct position (bellow equator line). I believe that is not happening with images from the northern hemisphere, but that is not a big problem, it is easy corrected with the subtraction of 10,000,000 to the Y (latitude) UTM value. The real issue came when you try to show in the same map window more than one image from different UTM zones. The first time you show, for instance images S-22-20_2000.sid and S-23-20_2000.sid (which includes most of S�o Paulo State), the images are correctly place into proper position, but if you zoom in into one of the above mentioned UTM zones (zone 22 is located at the West and zone 23 at the East side), then one image is correctly displayed but the other will be placed exactly on top of the first one, covering the correct with the one that belongs to the adjacent UTM zone. The mentioned situation does not occur when it is used Maptitude to show several MrSID images from the same zone. Do you have any suggestion or workaround to this problem? Thanks in advance for your aid. Best regards, Reinaldo ------------------------------------------------------------------------ berry_stewarttrancad wrote: >Hi Group: > >Maptitude 4.7 supports *.jpg files: > >The Joint Photographers Expert Group (JPEG) file format, named after >the committee that wrote the standard, is based on a mechanism >designed for compressing either full-color or gray-scale images of >natural, real-world scenes. It works well on photographs, >naturalistic artwork, and similar material; it does not work so well >on lettering, simple cartoons, or line drawings. JPEG handles only >still images (there is a related standard called MPEG for motion >pictures). Maptitude can use pictures and images stored in JPEG files >as layers in your map. > >JPEG is "lossy," meaning that the decompressed image isn't quite the >same as the original image. JPEG is intended for compressing images >that will be looked at by humans, because is designed to exploit >known limitations of the human eye; you are more sensitive to small >changes in brightness than to small changes in color. > >JPEG is a less-desirable image format than some others for two >reasons. It is slow to display, because the file needs to be reread >(starting from the beginning) each time a new portion of the image is >displayed. Formats such as ECW, MrSID, and TIFF are designed so that >portions of the image can be displayed by finding and reading only a >part of the file. Also, JPEG has a fuzzy appearance and limited >resolution, especially for large-scale display of map and other >images with linework and text. Formats such as ECW and MrSID provide >increasing levels of resolution as needed (to some limit) as you zoom >to larger scales. > >To use a JPEG file in a map with other geographic layers, it must be >accompanied by a JPEG/World (.JPW) file. This file contains >registration information for the JPEG image, and Caliper registration >information is added at the end of the file. The first time that you >open a .JPG file and its .JPW file, they must be in a folder to which >you have write access so that Maptitude can add the necessary >registration information. > >Stewart > >--- In [email protected], "Pam Lardear" <[EMAIL PROTECTED]> wrote: > > >>I just purchase an aerial photograph that I am trying to use with my >>Maptitude. It comes as a .jpg with a .jgw World file. Is there >> >> >any way to > > >>use this with Maptitude, or to convert it to the TIFF and TIFF >> >> >World? > > >> >> >>If not, can anyone recommend a good source for aerial photos that >> >> >work? > > >> >> >>This is from Terraserver. >> >> >> >>Thanks, >> >>Pam >> >> >> >> >> >>Pam Lardear >> >>Run River Enterprises >> >>http://www.runriver.net <http://www.runriver.net/> >> >>315-559-0526 >> >>"Helping you find your Way" >> >> > > > > > > > >Yahoo! Groups Links > > > > > > > > > > > ------------------------ Yahoo! Groups Sponsor --------------------~--> Has someone you know been affected by illness or disease? Network for Good is THE place to support health awareness efforts! http://us.click.yahoo.com/RzSHvD/UOnJAA/79vVAA/C5grlB/TM --------------------------------------------------------------------~-> Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Maptitude/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
