Re: [Xastir] Map Load Speed
Has anyone written any scripts to automate the splitting of shapefiles based on features used by Xastir at the different levels? -- William McKeehan KI4HDU http://mckeehan.homeip.net Follow me on twitter http://twitter.com/mckeehan On Sat, May 24, 2008 12:09 am, Tom Russo wrote: [snip] > To speed up rendering at high zoom levels, you'll have to create multiple > shapefiles with only features that are meant to render at close zooms, and > then exclude those shapefiles from being loaded at high zooms by using the map > properties. > [snip] ___ Xastir mailing list Xastir@xastir.org http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
Re: [Xastir] Map Load Speed
At zoom levels above 128 (or is that 128 and above?) I switch from TIGER shapefiles to national atlas shapefiles - there's a lot less data, so quicker drawing. http://nationalatlas.gov/atlasftp.html for some reason I used roads from NOAA instead of the national atlas. Don't recall exactly why, but I seem to remember lack of differentiation between road types (interstates vs. 2 lane roads, etc). dbfawks at http://www.eng.uah.edu/~jdw/xastir/ -Jason kg4wsv ___ Xastir mailing list Xastir@xastir.org http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
Re: [Xastir] Map Load Speed
On Fri, 23 May 2008, Tom Russo wrote: > To speed up rendering at high zoom levels, you'll have to create multiple > shapefiles with only features that are meant to render at close zooms, and > then exclude those shapefiles from being loaded at high zooms by using the > map > properties. There's another method that's a lot less work, but also much less flexible/desirable: Zoom way out, get the size of image you want, then create a snapshot of it. Save the snapshot and the .GEO file that matches it under new filenames. Set that map up to display when you're zoomed out, and the Shapefiles to display when zoomed in. You can of course modify this technique to multiple snapshots for multiple zoom levels, and panning left/right/up/down to create additional snapshots at each zoom. When zoomed out this will have the same advantages and disadvantages as other raster-format images, but when zoomed in you have the full capability of vector files. -- Curt, WE7U. archer at eskimo dot com http://www.eskimo.com/~archer Lotto: A tax on people who are bad at math. - unknown Windows: Microsoft's tax on computer illiterates. - WE7U. The world DOES revolve around me: I picked the coordinate system!" ___ Xastir mailing list Xastir@xastir.org http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
Re: [Xastir] Map Load Speed
On Fri, May 23, 2008 at 10:25:53PM -0400, we recorded a bogon-computron collision of the <[EMAIL PROTECTED]> flavor, containing: > Is there a way to speed up the loading of maps? Specifically, when I > use the line maps and dbfawk conversions it is wicked slow anytime I > am zoomed out beyond 64. The further out, the slower it is. It is > about intolerable beyond 128. So generally I keep it zoomed in to 64 > or less. Often that is good enough, but for a large scale event (like > the one I am to attend this weekend) I would like to see a broader > map without sacrificing speed every time I make an adjustment. Yes, but you have to do some work. The problem is that as you zoom out, more and more of the shapes in the shapefile are within the screen area, but the more you zoom out, the fewer of them are ultimately displayed due to settings in the dbfawk file. What is happening is that every one of those shapes is scanned and matched to the dbfawk file, and then discarded. To speed up rendering at high zoom levels, you'll have to create multiple shapefiles with only features that are meant to render at close zooms, and then exclude those shapefiles from being loaded at high zooms by using the map properties. For example, the TIGER/Line 2006_SE files with the stock tgr2shp.dbfawk file renders roads with CFCC values A1 to A3 at all zoom levels at or below 8192. CFCC values A31 through A36 are only rendered at or below zoom 256, and CFCC values A37 through A38 are only at zoom 128 or below. There are still other features that are only displayed at zoom levels of 64 or 96. You could use ogr2ogr and a "where" clause to create new shapefiles that contained only those features that should be rendered at 128 or below, only 256 or below, and above 256, then use the min and max zoom feature to exclude the low-zoom files completely --- they wouldn't even be scanned. This is a good bit of work to do, but if you really want fast map rendering, you have to make the job xastir is doing easier for it. It's doing a lot of file access and processing for every shapefile, and the farther you're zoomed out, the more work it's doing. That it's doing all that work only to decide not to display something is the issue, and the above technique will fix it. But the price is that you'll have split the monolithic county shapefiles As a quick example, you could separate out all of those roads that are supposed to be displayed at the high zoom levels (those with A1 and A2) with: ogr2ogr -where "CFCC like 'A1%' or CFCC like 'A2%'" output1.shp input.shp where input.shp is one of the TIGER 2006_SE polyline files. You could select all of the features that are NOT in that group with: ogr2ogr -where "CFCC like 'A%' and not (CFCC like 'A1%' or CFCC like 'A2%')" output2.shp input.shp Then tell Xastir to load output1.shp at all zoom levels, but output2 only at zoom levels less than 8192. That would eliminate all the local roads from those wide zooms, where they wouldn't be displayed anyway. Obviously, you'd have to do a *lot* more work than just those two extractions, since there are many more things that get decided by the dbfawk file. But that's how you'd go about it, using the dbfawk's "display_level" setting to guide you. -- Tom RussoKM5VY SAR502 DM64ux http://www.swcp.com/~russo/ Tijeras, NM QRPL#1592 K2#398 SOC#236 AHTB#1 http://kevan.org/brain.cgi?DDTNM "It's so simple to be wise: just think of something stupid to say and then don't say it." --- Sam Levinson ___ Xastir mailing list Xastir@xastir.org http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
Re: [Xastir] Map Load Speed
I have to tweak the .dbfawk files to eliminate what I don't want at which magnification. This is where I get the most speedup. 73 from 807, Richard, N6NKO Chip Griffin wrote: Is there a way to speed up the loading of maps? Specifically, when I use the line maps and dbfawk conversions it is wicked slow anytime I am zoomed out beyond 64. The further out, the slower it is. It is about intolerable beyond 128. So generally I keep it zoomed in to 64 or less. Often that is good enough, but for a large scale event (like the one I am to attend this weekend) I would like to see a broader map without sacrificing speed every time I make an adjustment. (I am using a high end Mac laptop for this, so I don't believe it is hardware related.) 73, --de Chip (N1MIE) FN41bn ___ Xastir mailing list Xastir@xastir.org http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir ___ Xastir mailing list Xastir@xastir.org http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
[Xastir] Map Load Speed
Is there a way to speed up the loading of maps? Specifically, when I use the line maps and dbfawk conversions it is wicked slow anytime I am zoomed out beyond 64. The further out, the slower it is. It is about intolerable beyond 128. So generally I keep it zoomed in to 64 or less. Often that is good enough, but for a large scale event (like the one I am to attend this weekend) I would like to see a broader map without sacrificing speed every time I make an adjustment. (I am using a high end Mac laptop for this, so I don't believe it is hardware related.) 73, --de Chip (N1MIE) FN41bn ___ Xastir mailing list Xastir@xastir.org http://lists.xastir.org/cgi-bin/mailman/listinfo/xastir
