MrSID MG4 LIDAR

STHSTH Global Mapper UserPosts: 434Trusted User
edited January 2010 in Suggestion Box
Regarding reading the new MrSID MG4 LIDAR - format (see this thread: http://www.globalmapperforum.com/forums/suggestion-box/4331-mrsid-files.html) it seems to read the new compressed "laser-sid" fine - however if I have understood correctly the new format support some kind of "overviews" like ECW and TIFF-files also may have (basically a downscaled version of the data for faster view). It does not seem however that this is supported at the moment for MrSID MG4 LIDAR and it loads all the data instead of these "overviews". If using overviews I would "guess" that large files would load as fast as small files and that when generating a 3D-modell from one of these layers instead of the complete layer it would take significantly less time.

Comments

  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited August 2009
    I'm not sure that something like that is available. Even if there was it really wouldn't fit the Global Mapper data model for vector data. It's easy to have different resolution layers available for raster data like imagery, but for vector data each point is a single point, it's not as easy to somehow group points for display. Right now the MG4 importer just brings everything in.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • STHSTH Global Mapper User Posts: 434Trusted User
    edited December 2009
    I have now loaded one of these new LAS-sid-files into GlobalMapper. I see they also mentioned it on their homepage: http://www.lizardtech.com/products/lidar/thirdparty.php

    Comparing it to loading with the free GeoViewer 4.0 from LizardTech (http://www.lizardtech.com/download/dl_options.php?page=viewers) the GeoViewer loads the file alot faster than GlobalMapper. I am not sure if it is possible with the released SDK from LizardTech to load the files "as snappy" as the GeoViewer 4.0?

    I assume you already know about LizardTechs "developercorner" http://www.lizardtech.com/developer/ - it might be an idea to ask there if it is possible to load the file "differently"
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited December 2009
    I believe the GeoViewer allows you to get a sub-sample of the data when zoomed out, whereas Global Mapper will read in every point in the Lidar data set when opened and internally create a point feature from it. This will make the load take a bit longer in GM as it needs to have all of the points available up front.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • STHSTH Global Mapper User Posts: 434Trusted User
    edited January 2010
    UPDATE:

    To partially load a file depending on the scale the instructions for doing that is referenced in this topic:
    http://www.lizardtech.com/forums/vie....php?p=712#712

    It mentions the PDF for the SDK with some examples on how to do this.
    __________________
    Sincerely yours

    Sigbjørn
    Norway
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited January 2010
    The link that you provided was apparently truncated by the forum so it doesn't work.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • STHSTH Global Mapper User Posts: 434Trusted User
    edited January 2010
    Sorry, here is the correct link:

    http://www.lizardtech.com/forums/viewtopic.php?t=270
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited January 2010
    That looks interesting. I think I can modify our import code to make use of that when you check the option to use preview mode. I'll let you know.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited January 2010
    I have implemented the change so now loading a MrSID LIDAR file with the preview option to just get every 10th point checked should be much faster. I have placed a new build at http://www.globalmapper.com/global_mapper11.zip with the change for you to try. Simply download that file and extract the contents into your existing v11.xx installation folder to give it a try. If you are using the 64-bit version, there is a new build available at http://www.globalmapper.com/global_mapper11_64bit.zip .

    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 January 2010
    Yes, now it loads much faster. I now load the SID-file containing approx 6 900 000 points. I set all points as LIDAR Ground Shot points and the correct elevation attribute. There is no "Loading 3D-model" in the 3D View, but after I wait quite alot of time the points are displayed.

    1. The points are not recognized as LIDAR Ground etc, but defaults to "Unknown Point Feature". Not sure if the attribute gets lost in conversion from LAS to SID or if GlobalMapper just does not pick up the attribute for each point.
    2. How can I "color the dots" according to intensity instead of elevation, while still maintaining the height of each point? (in 3D-view). The idea is to see the different features in the are and compare the vector-data with the LIDAR-data and visually see if there is a difference between these.
    3. Now only for instance every 10th point is loaded at start, and these are the points that are used - no new points are loaded as you zoom deeper? Loading an ECW "new" pixels are loaded for each zoom. I am not sure how many LIDAR-points can be handled simultaneously. But what about "reloading" the SID-file for each zoom-level? In that way you get more and more details as you zoom in?

    I will send an example file (original LAS, compressed LAS and vectordata) for download to your e-mail adress.
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited January 2010
    I took a look at your file. It looks like all of the points are coming in with a class ID of 1, which means unclassified. I was able to make the load even faster though in all cases (not just preview).

    I have placed a new build at http://www.globalmapper.com/global_mapper11.zip with the change for you to try. Simply download that file and extract the contents into your existing v11.xx installation folder to give it a try. If you are using the 64-bit version, there is a new build available at http://www.globalmapper.com/global_mapper11_64bit.zip .

    To color the dots by intensity you would need to use the Search Vector option to find all features with a particular intensity, then change the drawing style for those points.

    It is true in preview mode that just 1/10th of the points are loaded and that's it. No new points are loaded as you zoom in. While for raster formats it is relatively easy to dynamically fetch stuff as there is a fixed total pixel space to work in, for discrete vector data like Lidar points it would be a massive headache to try and dynamically pull in different data as you zoom in as there are lots of dependencies on a vector feature staying present once loaded until you unload the layer entirely. Maybe way down the road the architecture can be re-done to make this possible.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
  • STHSTH Global Mapper User Posts: 434Trusted User
    edited January 2010
    Fast as always (both adding the feature and the display of the files!) And it works great.

    Not sure if you have noticed these issues also?:
    1. The points are not colored in the 3D-view (even though they are colored in 2D-view)
  • global_mapperglobal_mapper Administrator Posts: 17,238
    edited January 2010
    The 3D view does not currently display point symbols (just black dots at the location). We hope to improve this in a future release.

    Thanks,

    Mike
    Global Mapper Support
    support@globalmapper.com
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