dhis2-devs team mailing list archive

[Jan Henrik Øverland <janhenrik.overland@xxxxxxxxx>]

Having 15 decimals is of course ridiculous in our case. The surface distance
per 1 degree change in latitude is approximately 111 km, so 15 decimals
means an accuracy of 0.000000111 mm. I think five decimals should be
appropriate (1 meter) or even four (11 meter) or three (111 meter)? Could
this be done during the db insertion?


2010/7/23 Knut Staring <knutst@xxxxxxxxx>

> 2010/7/14 Lars Helge Øverland <larshelge@xxxxxxxxx>:
> >
> > We are in the process of changing the GIS module in terms of how the
> > geographical information is persisted and presented.
> > In the snapshot version we now store the coordinates in JSON format
> directly
> > in the database on the OrganisationUnit.coordinates property. This gives
> us
> > a lot more flexibility in the way maps are presented.
> > Previously maps had to be registered explicitly either in the form of
> > GeoJson files or Shapefiles. Then the user had to select a map together
> with
> > indicator and period. Now the user can select an orgunit from a tree and
> the
> > children of that orgunit at the level below will be displayed in the map.
> > In large countries in India it is impossible to display a single map at
> the
> > lower levels (eg. for thousands of districts) as the map will be too
> heavy
> > and slow to load. Registering and managing maps for every e.g. provinces
> > will also be too cumbersome. With the current solution there is no more
> work
> > of registering and selecting maps - only the one time job of importing
> > geographical data/coordinates into the database.
> > Importing is a 4 step process:
> >
> > 1. Convert your shapefiles (or whatever format you have) into GML.
> > The recommended tool is FWTools, http://fwtools.maptools.org/ . The
> command
> > for converting shapefiles into GML is
> > ogr2ogr -F GML output.gml input.shp
>
> One problem is that the conversion to GML seems to generate very large
> representations, because the GML coordinates are output with 15
> decimals, whereas you would normally be happy with 5-6. Here is a
> comparison of what I get in GeoJSON vs GML (converting from the same
> shapefile):
> GeoJSON: 38.415412, 1.750212
> GML:        38.415411724082148,1.750212388592194
>
> It also seems that there the import process puts a bit too many
> brackets on points:
> Example point representation (which also has a ridiculous tail of
> decimals):
> [[[[37.270000000000003,-0.69]]]]
>
> Example full polygon representation (gets very big when adding
> hundreds of polygons into a layer):
>
> [[[[35.241617396557501,-1.042755167363498],[35.082178302163747,-0.910721897610392],[35.016946729972211,-0.895020643910023],[35.011665399182093,-0.885742630359804],[35.024369140812389,-0.87746378749961],[35.019944242042286,-0.853483690939046],[35.045208986632879,-0.856766680349123],[35.060339285653235,-0.839352562608713],[35.077610664723643,-0.860192408429204],[35.085033075563814,-0.846061280098871],[35.139987463515105,-0.881032254249694],[35.136418996765023,-0.843206506698804],[35.168249720175773,-0.842064597338777],[35.172674618945877,-0.792391540177609],[35.202078784966567,-0.793390710867632],[35.231625689657264,-0.819083671468237],[35.262599981047991,-0.804667065797898],[35.297285477858807,-0.830645503738509],[35.334540270729683,-0.814087818018119],[35.343961022949905,-0.790393198797562],[35.27601741602831,-0.724162455916004],[35.242759305917524,-0.747857075136561],[35.241331919217494,-0.694758289895313],[35.262029026367976,-0.680056206884967],[35.291861408398681,-0.655076939634379],[35.387496317300929,-0.65935909973448],[35.397773501541174,-0.647940006134211],[35.420611688741708,-0.729301048036125],[35.481989316843155,-0.77797493450727],[35.539513000854505,-0.798101086977743],[35.434029123722027,-0.895020643910023],[35.408478901791426,-0.957111965361483],[35.360233231330291,-0.98123480059205],[35.346673057679972,-0.973812389751876],[35.241617396557501,-1.042755167363498]]]]
>
> _______________________________________________
> Mailing list: https://launchpad.net/~dhis2-devs<https://launchpad.net/%7Edhis2-devs>
> Post to     : dhis2-devs@xxxxxxxxxxxxxxxxxxx
> Unsubscribe : https://launchpad.net/~dhis2-devs<https://launchpad.net/%7Edhis2-devs>
> More help   : https://help.launchpad.net/ListHelp
>