Register | Login
Attackpoint - performance and training tools for orienteering athletes

Discussion: Lidar file naming convention help

in: Orienteering; General

Feb 1, 2014 9:35 PM # 
cmorse:
Is there a standard convention for naming lidar data files in LAZ format?

I want to play around with some data in Kartapullautin, but its a large archive of tiles with no apparent reference map to allow me to select the tiles.

Tiles are 1000mx1000m

first two digits are '18' which I assume is the UTM zone.

digits 3-5 are alpha characters

digits 6-9 are numeric

This is different from the naming conventions I've seen in previous Lidar data I've accessed.

Metadata - though I couldn't see any obvious reference to naming convention.

Data Directory

Thanks in advance...
Advertisement  
Feb 2, 2014 12:51 AM # 
cedarcreek:
At the bottom there is a file called:

ftp://csc.noaa.gov/pub/DigitalCoast/lidar1_z/geoid12a/data/2598/tileindex.zip

Unzip that, and open the shp file as a vector layer in a GIS program---I use QGIS, which is free. Then you can use the information tool to get the names of specific tiles. (You can also download the four files near the bottom that are the shp, prj, shx, and dbf files, but whatever is easiest.)
Feb 2, 2014 1:32 AM # 
cmorse:
Was hoping to avoid installing a GIS package, but a viable option, thanks...
Feb 2, 2014 3:59 AM # 
cedarcreek:
I understand your reluctance, but it's incredibly useful to have GIS capability. Most of the data (lidar excepted on a technicality) is native to GIS anyway---georeferenced aerial photos, road shape file vectors.
Feb 2, 2014 3:10 PM # 
Tundra/Desert:
My experience has been that tiles are named every which way, adjoining counties in California use different conventions. There is some pervasiveness in the

AB
DC

or

12
43

patterns for quarter-tiles, but maybe they go counterclockwise, I gave up on finding "the" pattern a long time ago. Counties usually publish the overlay table with tile numbering but you really, really, really have to know where to look, I had to email the county in one case.
Feb 2, 2014 5:21 PM # 
cmorse:
I found a zoomable map that shows the tile boundaries, but no where does it identify them - clicking any of them in various ways simply shows the extent boundary of the entire dataset - ie all of eastern CT...
Feb 3, 2014 4:22 AM # 
cedarcreek:
Can you tell me what area you need? (Like a park name or a gmaps-pedometer outline?)
Feb 3, 2014 10:22 AM # 
cmorse:
Installed QGIS yesterday, will go that route. Was having server timeout issues with ftp site so haven't grabbed shp files or any data yet... thx
Feb 3, 2014 1:39 PM # 
Terje Mathisen:
Most tile naming schemes I have seen are based on some form of modified Hilbert curve, i.e. using alternate (groups of) bits from the x ((Easting) and y (Northing) direction.

By far the easiest way to handle this though is to download lastools and use lasinfo to extract header info for each tile. :-)

Next, if you want to do anything at all with the Lidar you should use lastile to convert the input data into relatively small tiles with a boundary area around each of them (I use 25x250 m tiles with a 32m boundary), this way to can work with each tile separately and still avoid pretty much all boundary glitches along the original tile boundaries.
Feb 3, 2014 1:42 PM # 
Terje Mathisen:
A little PS to my previous post:

Here is the perl function name2utm which takes as input the name of an ortophoto tile from Finland and returns the UTM coordinates):

sub name2utm
{
my ($name) = @_;
return undef unless ($name =~ /^([L-M,P-X]\d[1-4]{3}[A-H])/i);

$name = $1;

my ($e, $n) = (500000, 6960000); # Use P5111A as starting point!
my $c = ord(uc(substr($name,5,1)))-ord('A');
$e += ($c >> 1) * 6000; # Two top bits for East
$n += ($c & 1) * 6000; # Bottom bit North
# Bottom layer (A-H) encodes 4x2 blocks, so scale the rest by this amount:
my ($esize, $nsize) = (6000*4, 6000*2);
# Each of the three previous digits (1-4) encodes two bits:
for (my $p = 4; $p > 1; $p--) {
$c = ord(substr($name,$p,1)) - ord('1');
$e += ($c >> 1) * $esize; # Top bit Easting
$n += ($c & 1) * $nsize; # Bottom bit is Northing
$esize *= 2; $nsize *= 2;
}
# Second char (a digit) is the final Easting coordinate:
$c = ord(substr($name,1,1)) - ord('5');
$e += $c * $esize;
# First char in filename (L-M,P-X) is final Northing offset:
$c = ord(uc(substr($name,0,1))) - ord('P');
$c++ if ($c < 0); # Code 'O' is unused!
$n += $c * $nsize;
return ($e, $n, $name);
}
Apr 29, 2017 4:44 PM # 
cmorse:
Old thread, but adding this note in case I need to find it in the future.

Handy online tool for quickly viewing SHP files and their underlying data, without requiring a GIS installation...

that is all...

Please login to add a message.