[Xastir] maps

[Brian D Heaton]

Tim - 

	Comments in-line below...

On Wed, 2004-02-25 at 12:38, tbaggett at jump.net wrote:
> 
> Thanks for the reponses. I will reply to several comments and questions at once below.
> 
> -- Tim
> 
> 
> Matt Werner:
> > Why not download the shapefiles already made?  
> > esri.com has them in layers by state or county.
> 
> Because I can only download them one county at a time, or one layer per state at a time, and there is a daily download limit. I prefer to automate and batch things when possible.
> 
> To obtain the Tiget 2002 map file, I simply initiated a wget and went to bed. The next morning, 5GB of compressed tiger files were on my hard drive.
> 
Agreed 100%. I did exactly the same thing.


> Similarly, the TGR2SHP conversion tool can batch the conversions.
> 
> 
> Matt Werner:
> > I have shapefiles from Tiger data (obtained from ESRI).  I have about 7-10
> > layers (not sure - I'd have to check) for all of MN, WI, and the UP of MI.
> > I have map layers set up so that when I'm in closer, I'll get roads, urban
> > areas, lakes and rivers, railroads, and maybe one or two other things.
> ...
> > The biggest hassle
> > for me was to get them all on the hard drive, in some sort of order, and
> > then to set up the map chooser. 
> 
> Yes, I would like to find a way to distribute maps with corresponding dbfawk files, and layer settings, rather than having it in a global map.sys file (I think that's the name).
> 
> I have done similar to what you have done, but I would like to be able to turn off local roads at greater zoom levels, but still having major roads displayed.
> 
> My current idea for doing this is to seperate the major roads from the local roads in the Tiger file, then create two seperate shapefiles for roads.
> 
If you take a look at the actual format of the TIGER data the value to
use is the CFCC (Census Feature Class Code).  There are different values
for different road types.  If TGR2SHP will let you set the min/max CFCC
values you can split the road data into 2 or more files.  

> 
> Curt Mills:
> > There should be no restrictions on the size of the map either,
> > except for your loading time and storage requirements.  Xastir
> > should handle it.
> 
> 
> This is good to know.
> 
> Storage is typically not a problem. I was quite shocked to see 200 GB Hitachi hard drives at Fry's for $99!
> 
> However, I am concerned about loading time. Do you have any suggestions for optimizing the map layouts so the loading time can be reduced? 
> 
> 

I think the first idea is that there is no such thing as too much RAM. 
The second is to look at splitting the TIGER shapefiles into smaller
chunks by a fine grained look at CFCC.  It makes a larger set of files,
but the additional granularity is a win.  Once you have a more granular
set of shapefile the user can customize the map levels such that only
what is relevant at a given set of zoom levels is displayed.  This way
you aren't loading a bunch of stuff that you can't see or make use of at
a given zoom level. 

> Curt Mills:
> > Assuming the end product is quite satisfactory, mind sharing those
> > out to other Xastir users?
> 
> Absolutly! 
> 
> However, before doing so, I would like to make sure it is something that is distributable and clean. Right now the problem is distributing dbfawk files and layer settings, and the shear volume of the mountain of data. I am examining the feasibility  of a script that can go through the Tiger map files and strip out the unneeded things we don't care about, like fences.
> 
> I'll say right now, I have a whole new level of appreciation for the map vendors who simply take the Tiger map database and package it up for us (i.e., Delorme). They fit the entire US on a single CD, optimized for quick rendering on a PC.
> 
> I will admit straight up that I don't have a clue what I am doing, and have only started picking this stuff up in the last few weeks.
> 
> 

Ideally, we'd store these shapefiles in the APRS-MapManager.  The dbfawk
files and recommended map levels could be part of the Xastir package
since that data is application specific.

> Tom Russo:
> > I have 33 shapefiles converted from tiger data.
>  <...>  
> > That covers all counties in New Mexico. 
> 
> Hi Tom, the only state which I referred to having converted from Tiger to shapefile was in fact NM, and I've been to your (interesting) website.
> 
> 
> Tom Russo:
> > I rarely have the program
> > zoomed out to cover the whole state, and I use agressive map levels to keep
> > render time short.  Even so, it is slow to display the entire state.
> 
> Yes, this is my experience as well. Plus, there will be times I want to display multiple states. Granted, I may only want to show urban areas, major roads, and major hydrology, but the loading time is what I think I may be facing.
> 
> There is no need to render the fenceline around Kirtland AFB at every zoom level - if any! Ditto for the tramway.
> 
> 
> 73,
> Tim
> Austin, TX
> 
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Brian D Heaton
Senior Network Engineer
Janus Research Group
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