Slow raster redraw

kfroesekfroese Geotechnical EngineerPosts: 161Trusted User
edited October 2009 in Technical Support
Between yesterday and today, using the same dataset and same Global Mapper build, I've had a sudden drop in redraw speed. I am using a map catalog to handle the rasters (about 12 satellite images) and even tried dropping the catalog in favour of loading image by image manually as needed. But the panning speed is still quite slow (on a duo core machine with 2Gb of RAM). The images are now saved on my hard drive rather than pulling from the company network but that hasn't improved the speed appreciably. Same thing with running only Global Mapper and closing other notorious memory pigs like Outlook. Any thoughts on where my sudden lag has come from? I'd appreciate any and all suggestions.

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited September 2009
    That's strange, especially if you are using the same build and moving the files to your local hard drive didn't help (did you update the map catalog to point at the local files after you moved them?). What format are the files display in the map catalog?

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • TeeGeeTeeGee Global Mapper User Posts: 61Trusted User
    edited September 2009
    I have the same configuration (duo core machine with 2Gb of RAM) and get the same problem sometimes. For me, the problem is always solved with a system reboot (after closing GM). When Windows closes before reboot, there is a warning : "insufficient memory space".

    TeeGee
  • STHSTH Global Mapper User Posts: 434Trusted User
    edited September 2009
    One thing that bumps into my mind - are you using exactly the same coordinate system in Tools - Configure - Projection as the Options in the MapCatalogue?

    When there is a difference between the coordinate systems for raster files and the "view (Tools-configure-projection)" I have experienced slow speed due to reprojection. However putting the view (tools-configure-projection) to the same coordinate system as the input rasters makes them draw faster.

    Also if you turn on "transparent background" on the rasters they redraw slower because GM needs to find which pixels to make transparent for each redraw - so check that transparent pixels are also turned off. (This is also true to Transparency - as it needs to read each pixel to set the transparency - try to set this to OFF also).
  • kfroesekfroese Geotechnical Engineer Posts: 161Trusted User
    edited September 2009
    Thanks to the community for suggestions. I did check - the geotiff map catalog is in the same projection as the project though some of the vector files are not. I don't think that is the problem as there are certainly no redraw issues when the tiff layer is turned off. I did have the catalog set to about 70% transparency as I was overlaying it on some airphotos. Changing the transparency didn't help with the redraw.

    To further complicate the problem, this isn't a consistent issue. Sometimes it runs fine, sometimes it doesn't. Sometimes it starts pretty slow but suddenly, an hour or two later, it improves and I'm off to the races again. I have tried shutting down various other programs I generally have open (Outlook, Foobar, Rainmeter) but that doesn't seem to consistently fix the problem either. If I copy the matcatalog to my hard drive, that doesn't usually fix the problem either. I'm kind of at a loss. I'm running at 63% of my 2.0Gb RAM and 38% of the total 3.3Gb swap file and generally no more than about 10% of either of the two CPUs except during the redraw. Redraw, when it's lagging, pushes both CPUs to between 50 and 100% utilization. Not sure what happens on redraw when it's not in a laggy mood. I'll edit this post with that detail once it gets over its morning dragging (it's laggy badly again this morning).
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited September 2009
    Are you using enough memory to go beyond your actual physical RAM? If so that can slow things dramatically as a swap file is much slower than actual physical RAM. I don't know if it is possible for you, but if you can upgrade your RAM to 3 or 4GB you can likely get much better performance. Even better would be to go to 64-bit Windows and a 64-bit version of Global Mapper as you could then use more than 4GB of RAM.

    Let me know if I can be of further assistance.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • STHSTH Global Mapper User Posts: 434Trusted User
    edited September 2009
    I had a pretty decent computer also (3 GB RAM, approx 2 GHz dual core) - however it started to crash when working with really large datasets. This was due to the using the swap on the harddrives. The harddrives were old ATA-disks and very slow due to age and defragmentation. Since Task Manager does not show anything related to disk read/writes I recommend you to take a look at Free Extended Task Manager (http://www.extensoft.com/?p=free_task_manager). When you experience this lag you can open Free Extended Task Manager and see if it is writing/reading alot of data in the Disk I/O graph (if you hoover on top of it you see even which progress is accessing the disk). If you see that GlobalMapper is using Disk I/O alot during these lags I would assume it is using the SWAP and that this is the case things slow down.

    Working with large datasets I would recommend 64-bit Windows XP (or Vista if you have to...) just because of the amount of data you can then load. I recently loaded a large set of data (LAS and DGN files) and GlobalMapper crashed - when looking at memory usage it used 8 GB of 8 GB available so that was no surprise :).

    Online imagery: Hm, one more thing swifted my mind: Do you have any layers from the " File - Download Online Imagery" - option? If yes, try to either save these locally or remove them to see if it helps.

    Create overviews on GeoTiffs: Another thing you might try is to create Overviews on the GeoTiffs if they do not already include that? In that way you might also be able to open all 8 files without any MapCatalogue but using the files themselves.
  • kfroesekfroese Geotechnical Engineer Posts: 161Trusted User
    edited September 2009
    STH: Thanks for the tips.

    I've checked a few more things.
    1. Panning/redraw becomes at issue at zoom scale of 1:9449 or larger (yes, it took a few tries to pin that number down!).
    2. This applies regardless of how many of the layers I have turned on or loaded. I took the project down to just two satellite images and still had the redraw lag at the same zoom scale. Slightly faster, but only slightly.
    3. I installed the recommended Extended Task Manager (which is not free but provides a 2 month trial) and checked Disk I/O. With just the two satellite images open, Disk I/O held steady at about 1.1Gb until the redraw finally completed. With full project open, this increased to 1.4Gb during redraw. No other applications were running. At a scale of 1:9000 (below the magic threshold), Disk I/O increase during redraw was negligible.
    4. Online imagery is not loaded. All the stuff I have loaded is off of network drives (1Gb connection).
    5. I am not familiar with this Overviews you refer to. Can you be more specific?

    This is starting to look like a hard-drive swap file issue or that I need more RAM (who doesn't?). I'd love to go to a 64-bit processor but I got this computer about 5 months ago so don't expect the company will spring for another new machine.

    Thanks for the help and suggestions. I'll defrag the HD tonight and see if that helps.
  • kfroesekfroese Geotechnical Engineer Posts: 161Trusted User
    edited October 2009
    I seemed to have corrected the problem. First, I changed the swap file size which forces a dump-and-reopen of the swap which helped. Win XP defrag appeared to be relatively useless (I miss the days when you could run defrag before the full OS had a chance to get up and running and tie up big files effectively preventing things like the swap file from getting optimized). These were only minor tweaks. The big boost in performance came when I removed a bunch of layers from GM - dumped 3 NTS sections worth of DEM and about 10 scanned airphotos (about 2.5Mb each). After saving and reopening the project, it runs much better.

    I'm still confused how the problem started as I used to be able to run that much stuff without lag. Anyhow, the problem is resolved and as soon as our pre-order Win7 discs arrive, I'm upgrading to 64-bit to properly utilize the duo core chip in this machine.
  • STHSTH Global Mapper User Posts: 434Trusted User
    edited October 2009
    For defragmenting I would recommend the free DeFraggler which works alot better than Windows built in and you actually see which files are fragmented.

    http://www.defraggler.com/
    I'm upgrading to 64-bit to properly utilize the duo core chip in this machine.
    Hm, will the upgrade to 64-bit make you able to use more CPU? I do not think so. GM 32-bit will use all CPUs available. Will it make you able to use more than 4 (3) GB of RAM? Yes definitely. GM still uses only 1 instance per physical CPU (one physical CPU can have 1, 2 +++ Cores - One CPU can have 1, 2 +++ CPUS - not a very good explanation though.. :))
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