[Xastir] maps

[Chris Bell]

> 
> > 1) What is the maximum number of maps (# files and file sizes) that people
> > have realistically used with Xastir?
> 
> Ask Chris Bell.  I think he holds the record at # of maps, in the
> thousands easily.  I'm in the several hundred range, but haven't


Yeah, that would be me... 
about 1500 shape files (all of CA AZ NV) from esri (about 1.5 Gb), 
173,192 (!!) jpg files from the topo! for CA (four resolutions) (about 8 Gb)
about 1000 other maps, (radar urls, pocket, dos, GNIS, etc.)
8 Gb of DRGs for AZ that I have not sorted through yet
1 Gb of DRGs for CA that I don't use since I have the topo! jpgs
600Mb of DRGs for NV that have messed up geo data 

I would also love to see some sort of map-set-bookmarks function.  I
love the map display bookmarks, I use them A *LOT*.  It is so nice to
be able to jump from one spot to another when testing maps and code...

My typical usages: 
1. a small set of shape layers (place,water poly,roads,designated points) 
   plus GNIS points for quick navigation while driving.
2. 24k and/or 100k topo maps while exploring/camping off in the desert and mountains
3. combos of all sorts of things while planning a trip 

The large number of maps does become a problem of time... I never use
the full set of topos, to index a 78409 subset of maps took my 1Ghz
laptop about 1 hour to re-index.  Then pulling up the map chooser window
takes minutes to build the list of files.  Fortunately I can
not-expand the directories so it pops up really fast, and it is easy
to select a few top-level directories and away we go.  Also, the
newish mod to have the map-properties window only act on the selected
list makes updating layers really easy... select a directory, hit
properties, select all, update, done!

I use symbolic links (ln -s) and directory permissions to
enable/disable groups of maps sometimes.  My topo collection is so
massive, I have a directory in my maps directory called "topo".  If I
don't want to wait for their re-index, I just `chmod 000` that top
dir, and they all dissappear.  Inside "topo" I have links to the
individual regions (actually the orignal cdrom images, kind of like
counties) that are stored on a different (bigger) disk partition.  I
can add or remove these links to enable/disable the different regions.
I recently changed that scheme somewhat.  Now I added another layer of
subdirectories for each resolution, and the links inside them point to
the specific directories (24k or 100k or 250k) instead of the whole cd
that has all of them.)  This now lets me choose a resolution all at
once instead of relying on map zoom limits to select the proper map.

In case you are wondering why I would be re-indexing so often... I
have a lot of maps stored on an external (USB) hard disk, that is not
connected all the time.  Also, as a developer, I am often testing new
maps, and specific bugs/features in certain maps.  I often want to cut
down on the quantity of data to speed up test cycles.  

WARNING... reindexing to remove some maps will remove any layer/zoom
properties you set for them...  

So, my recommendations for large quantities of map data:

1. subdirectories - seperate types of data, and layers to make it easy
to select groups at once.

2. map files - make them smaller regions.  the geo extents make loading several small regions much faster than one big file.  (so make counties or smaller instead of the whole state at a time!) 

3. layers - (data content) Seperate them out, and put them in the
subdirectories above for easy selection of content for the current
mission.

4. display layers - spend some time playing with the stacking of the
maps, and figure out a good system.  Unfortunately labels are drawn at
the same time as their feature, so subsequent layers can obscure lower
labels.

Chris.
KD6ZWR
cbell at junknet.com