This will allow you to select and plot each feature and see if your numbers are what are expected
The problem was not with unpacking the data - it was with my understanding!!!
I had erroneously thought that the envelope would be the bounds of the UK. Whereas, it is only the bounds for a single route! The decimal places in the coordinates still confuse me but rounding them gives sufficiently high accuracy.
My test code looks like this:
This shows clearly what is happening and has allowed me to pick the data structure apart a bit at a time. The output I get is:use DBD::SQLite; use Data::Dumper; use strict; use warnings; my $dbh = DBI->connect("dbi:SQLite:uri=file:osopenusrn_202203.gpkg?mod +e=rwc"); my $tab = $dbh->prepare("SELECT * FROM openUSRN LIMIT 1"); $tab->execute; my $data = $tab->fetchrow_hashref; my $geo = $data->{'geometry'}; my @test = unpack "(H2)2 CCVd6CVVCVV(d<)6CVV(d<)9", $data->{'geometry' +}; print "\n\nUSRN\t\t" . $data->{'usrn'} . "\n"; print "\nMagic bytes\t$test[0] $test[1]\n"; print "version\t\t$test[2]\n"; print "flags\t\t"; printf("%08b\n", $test[3]); print "SRS ID\t\t$test[4]\n\n"; print "minx\t\t$test[5]\n"; print "maxx\t\t$test[6]\n"; print "miny\t\t$test[7]\n"; print "maxy\t\t$test[8]\n"; print "minz\t\t$test[9]\n"; print "maxz\t\t$test[10]\n"; print "-----\n"; print "NDR\t\t$test[11]\n"; print "type\t\t$test[12]\n"; print "number\t\t$test[13]\n\n"; print "byteOrder\t$test[14]\n"; print "type\t\t$test[15]\n"; print "number\t\t$test[16]\n\n"; #print "byteOrder\t$test[17]\n"; #print "type\t\t$test[18]\n"; print "Point1 x\t$test[17]\n"; print "Point1 y\t$test[18]\n"; print "Point1 z\t$test[19]\n"; print "Point2 x\t$test[20]\n"; print "Point2 y\t$test[21]\n"; print "Point2 z\t$test[22]\n\n"; print "byteOrder\t$test[23]\n"; print "type\t\t$test[24]\n"; print "number\t\t$test[25]\n\n"; print "Point1 x\t$test[26]\n"; print "Point1 y\t$test[27]\n"; print "Point1 z\t$test[28]\n"; print "Point2 x\t$test[29]\n"; print "Point2 y\t$test[30]\n"; print "Point2 z\t$test[31]\n"; print "Point3 x\t$test[32]\n"; print "Point3 y\t$test[33]\n"; print "Point3 z\t$test[34]\n";
USRN 4601764 Magic bytes 47 50 version 0 flags 00000101 SRS ID 27700 minx 637590.385 maxx 642426.601 miny 309577.58 maxy 310361.391000001 minz 0 maxz 0 ----- NDR 1 type 1005 number 34 byteOrder 1 type 1002 number 2 Point1 x 640921.438 Point1 y 310210.692 Point1 z 0 Point2 x 641634.2632 Point2 y 309910.6438 Point2 z 0 byteOrder 1 type 1002 number 3 Point1 x 637969.3747 Point1 y 309910.6438 Point1 z 0 Point2 x 638226.29 Point2 y 309978.609999999 Point2 z 0 Point3 x 638404.534 Point3 y 310054.294 Point3 z 0
I've sanity checked the data against online tools. First I looked up the USRN of the first entry in the database. I then plotted the 5 points I got from the first 2 of the 34 LineStrings. All 5 points are on the route shown by the USRN so I take that a success :)
Of course, I still need to generalise the reading of the different geometry data types but at least their structure makes some sense.
The first step is to get the midpoint of each USRN. Just taking the centre of the envelope should provide this and won't require too much delving into the geometries - although that will have to follow in time.
Lots of thanks for your excellent pointers.
In reply to Solved! (was: Re^10: Geo Package files)
by Bod
in thread Geo Package files
by Bod
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