Optimisation is the act of making things as good as possible with regard to some criterion, eg. more efficient, faster or slimmer.

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35
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3answers
6k views

Are there newer routing algorithms (than Dijkstra, A*) in GIS databases?

There are works like Reach for A* from Microsoft researchers and Highway Hierarchies by Sanders and Schtolz (if I spell the name correctly) from Karlsruhe Uni. Both of them reduce the calculations ...
22
votes
5answers
8k views

Optimizing osm2pgsql imports for OSM data

I'm currently building an instance on EC2 on which to import the entire Planet.osm snapshot of the whole Earth's worth of data for some projects we're working on. I've spun up a large Ubuntu x64 ...
19
votes
2answers
5k views

Looking for fastest solution for Point in Polygon analysis of 200 million points

Apologies for asking a question that has been asked before -- I've read through answers, and I'm left wondering how to implement the recommendations. I've never used SQL, Python, C, and have only ...
17
votes
6answers
6k views

Ways to Speed Up Python Scripts Running As ArcGIS Tools

This is a pretty general question. I just wondering what tips and tricks GIS programmers have used to speed up arcpy scripts that you import into the toolbox and run. I work most everyday writing ...
16
votes
7answers
2k views

Fastest way to spatially join a point CSV with a polygon Shapefile

I have a 1 billion point CSV file and a shapefile with around 5,000 polygons. What would be the fastest way to spatially join points and polygons? For each point, I need to get the containing polygon ...
14
votes
1answer
161 views

Alternative indexing methods for point set operations

It is common to use a bounding box spatial index to improve performance when working with a large number of features. Where operations are performed against individual geometries with a large number ...
12
votes
2answers
1k views

How to equalise colour, brightness and contrast across several scanned paper maps

I am a vectors guy mostly, but for a current project I need to work with a bunch of old scanned paper maps (ww2 bomb damage maps for London, if your interested!) We scanned and georeferenced the ...
11
votes
5answers
2k views

Speeding up OpenStreetMap PostGIS querying

I have OpenStreetMap data for the Netherlands loaded into a PostGIS database (PostgreSQL 8.3 / PostGIS 1.3.3) using the osmosis schema. This means all tags are stored in a hstore field. In addition to ...
10
votes
3answers
1k views

optimize nearest neighbor query on 70 million extremely high density spatial point cloud on SQL Server 2008

I have about 75 million records in a SQL Server 2008 R2 Express database. Each is a lat long corresponding to some value. The table has geography column. I am trying to find one nearest neighbor for a ...
10
votes
1answer
323 views

Are there any intelligent travelling salesmen?

Jokes aside, I have had a routing problem that is almost a travelling salesman problem (TSP): the starting point is defined the end point coincides with the starting point each node has to be ...
8
votes
4answers
1k views

Fastest spatial storage format?

I am wondering what storage method will result in the fastest reading of the map vectors for rendering. SHP? PostGres? SQLite? (They do not change often and I do not need spatial functions for these ...
8
votes
4answers
1k views

Best way to find the polygons crossed by a line

I'm trying to find all the polygons crossed by a single line (a GPS track). I'm using the OGR library (from python) for computing this, but it's currently a bit 'brute-force' (and slow). For every ...
8
votes
2answers
2k views

How can I more efficiently select related records?

Below is the code I'm using to replicate the "related tables" button in ArcMap. In ArcMap that button selects features in one feature class or table based on the selection of features in another ...
8
votes
4answers
1k views

Performance of google map tile creation processes

I know that question is rather vague but please bear w/me. I'm trying to get an idea of what sort of product performance - specifically timing - people have seen for various methodologies they have ...
8
votes
2answers
527 views

How to speed up space partitioning in postgis?

I've a bunch of overlapping polygons and I'm trying to partition the space to avoid having overlapping ones. I think my problem is fairly simple. Using some ESRI product and ...
7
votes
3answers
2k views

how to find 20 closest points efficiently

Say I want to find 20 closest business near me. My table structure is like this: BusinessID varchar(250) utf8_unicode_ci No None Browse distinct values Change Drop ...
7
votes
3answers
3k views

Poor Performance when using Spatial Indexes in MySQL

Re-post of a question asked on Stack Overflow when it was suggested this would be a better forum. I'm trying a little experiment at pushing a data set which is not geo-spatial but fits it quite well ...
7
votes
1answer
194 views

Optimize GEOSGeometry's spatial operations by avoiding thread-safety checks

A ranking algorithm I'm developing for a Django webapp requires performing spatial operations (within, intersections, sym_difference, etc.) using a query against large number of geometry objects. ...
7
votes
2answers
175 views

Algorithms for optimally locating points

I am trying to compare locations of where several thousand facilities have been actually built to where they would be optimally located to minimize travel times of the population (represented by ...
6
votes
1answer
1k views

Performance Gain Through GIST Index for Point in Polygon Query

I have two tables: locations(id,region_id,the_geom) and regions(id,the_geom). For each location point I want to determine the region it is located in: UPDATE locations SET region_id = (SELECT id ...
6
votes
1answer
536 views

PostGIS query vs QGIS filter

I have a PostGIS dataset with around 3 million shapes. I only need to view about 1,500 of these shapes at any given time, but the shapes I need to see depends on which feature is selected in a ...
6
votes
5answers
1k views

Effectively displaying a large amount of data on Google Maps APi

I have about 20 layers that I'd like to put on a Google maps API. I assume I'll need some form of a tile cache server and perhaps under mapserver or geoserver. These layers amount to about 400mb so ...
6
votes
1answer
566 views

Is there anyway to make GPModels with python scripts execute faster?

I do not know if anyone else has this problem but my GPModels that include simple python scripts seem to take way too long to execute. One example is a model I built which is a simple select feature ...
6
votes
1answer
1k views

How to Optimize Openstreetmap Tile Rendering?

I am currently trying to render Water (3,198,333 records) and detailed world borders (processed_p) for the world. I am successful in rendering both layers, but I am not happy with performance. My ...
5
votes
2answers
2k views

Geoserver WMS tile rendering is too slow

I have following geoserver status. I have installed JAI but memory used by jai is 0 and image rendering for wms is very slow. Is it issue with memory allocation? I am using Sql server 2008.
5
votes
3answers
3k views

Slow IE8 responsiveness with OpenLayers and many features

Background Adding about 700 sites to an OpenLayers Map. Firefox 11 and Google Chrome display the sites just fine. IE8, which is the organization's standard and will not be upgraded for the ...
5
votes
4answers
3k views

ST_Intersection slow query

I am trying to perform an intersection between two layers: Polyline layer representing some roads (~5500 rows) Polygon layer representing irregularly shaped buffers around various points of interest ...
5
votes
1answer
361 views

What is the best way to prepare digital orthophotos for the web?

My system: Linux Ubuntu 10.04 server (100gb: 4gb RAM: 32bit) /tomcat6/geoserver/geowebcache/FWTools My Objective: Create Aerial Photo coverage in ETRS89 N32 My Data: 1300 3 band Orthophotos in Tif ...
5
votes
1answer
137 views

Optimize the locations of 2 additional restrooms on a trail (ArcGIS 10.2)

In the image below, the line is a trail and the point is an existing restroom. I would like to find the rough locations of 2 additional restrooms that minimize the maximum distance along trail from ...
5
votes
1answer
518 views

Speed up pgRouting point_to_id using new <-> operator in PostGIS 2.0.0

The point_to_id function, which assigns a node id to a point based on existing nodes and tolerance, is using a query as follows: SELECT id, the_geom FROM vertices_tmp WHERE ...
4
votes
2answers
900 views

Qgis is slow with complex 'postgis query' layer. How to speed up?

I have a postgis layer in Qgis that is a result of a complex query. Every screen update, Qgis runs the Query again and that's slow. Any suggestion on how to speed up? EDIT - Here is the query: ...
4
votes
1answer
121 views

Which spatial bundling or grouping algorithm optimally groups elements by attribute?

As I delve deeper into GIS, I find myself trying to improve efficiencies of certain procedures and processes. The one process I'm working on now is spatially scheduling construction projects. For ...
4
votes
2answers
312 views

How do I reduce the number of drawn polygons on an Android Map?

We're using spatialite-android and Nutiteq to render Archaeological datasets. One of our sample data sets has 7000 polygons that turn into 400,000 objects in our renderer. Is there a common GIS ...
4
votes
1answer
489 views

Shorter Version of this SpatiaLite Query

I've been doing some spatial queries using spatialite, and they're large enough that a spatial index becomes a must. An example of using an index is given in the tutorial spatialite> SELECT ...
4
votes
2answers
312 views

Fastest way to remove matched points

Hoping someone can see a faster way of doing this, because at the moment I'm averaging 9 hours per run for what I'm trying to do and well basically getting my behind chewed off by the boss :-) The ...
4
votes
3answers
447 views

How to efficiently find points within an elliptical area?

Using PostGIS 2.0.0 I need to filter the results of a function, which returns many POINTs, to find the ones that lie within an elliptical area defined by two points and a distance (all parameters ...
4
votes
1answer
258 views

meeting point minimizing travel distance for participants?

The problem is to find the point minimizing the travel distance for around 100 persons in different regions who want to meet in the same place. Travel is by car not by plane. Assuming that I get ...
3
votes
3answers
3k views

How to fix performance problem in PostGIS ST_Intersects?

I'm a newbie in postgis and I have a problem in query performance. This my query: SELECT DISTINCT ON (userid) userid ,ST_AsText(position), timestamp FROM table1 WHERE ST_Intersects ( ...
3
votes
2answers
1k views

Postgres/PostGIS Spatial Query Performance Problem

I have a query in Postgres/PostGIS that I am a bit confused about. The spatial intersection happens very fast, ~ 2 seconds for 10,000, but the update takes > 15 seconds for the same number of points. ...
3
votes
1answer
234 views

geodjango slowness and debugging

I'm using geodjango + postgres to display polygons from tigerline on a map. Pretty simple stuff so far. My issue is that when I use the GPolygon object: django.contrib.gis.maps.google.GPolygon there ...
3
votes
2answers
378 views

PostGIS - ST_Collect but only include POLYGONs not POINTs?

In PostGSI, is there anyway to turn a GEOMETRYCOLLECTION into a MULTIPOLYGON by dropping all non-POLYGONs/non-MULTIPOLYGONs? I'm doing a query that cuts a bunch of geometries (using ST_Intersection) ...
3
votes
0answers
69 views

District heating expansion design with ArcGIS [closed]

I am quite new at GIS but I have some experience of the basic concepts involved in a workflow of them. What I currently want to do is to calculate the cost of expanding an existing district heating ...
3
votes
0answers
258 views

Shortest distance from pgrouting with cost not being length: optimal solution

I'm using pgrouting shortest_path_astar with a complicated cost function. It gives back the edges, vertices and costs. I would like to get the total distance of this shortest path (i.e., the sum of ...
3
votes
0answers
136 views

how to increase request feature speed?

I use Geoserver with Oracle DB. Amount of records in DB is less than 4000, but feature request takes 5-6 seconds. How can I speed up this? P.S. Native JAI is false in my Geoserver UPDATE: I have ...
2
votes
2answers
1k views

How to optimize a WMS request by limiting number of tiles?

I want to display the layer using WMS and meanwhile I want to limit the number of tiles with their respecive BBox when map is loaded. At the backend I am using geoserver. I can limit the number of ...
2
votes
2answers
360 views

How to draw one rectangle in ArcObjects?

Is there button in ArcObjects "draw rectangle" such as in openlayers? Update Well, I use this code for drawing: ESRI.ArcGIS.Display.IScreenDisplay screenDisplay = Map1.ActiveView.ScreenDisplay; ...
2
votes
3answers
204 views

Looking for TSP with Target different from Source

I know the TSP (traveling sales person) in osm2po is beta but it works quite well. Is there a way to designate a final target location that is different from the initial source location. In other ...
2
votes
3answers
181 views

How does Jenks optimisation method assist in ESRI mapping?

Why would someone use the Jenks optimisation method in ESRI mapping? What would be easily located or discovered with this analysis?
2
votes
1answer
283 views

Find nearest neighbours faster in PostGIS

I currently have a query that calculates the number of useful amenities within a certain radius of each town, using OSM data: create table places as select town.name, place, town.way, ( select ...
2
votes
1answer
533 views

How to speed up this simple MySQL points in the box query

MySQL doesn't have nearest neighbor search so. So I try to come up with a "distance" that's reasonable so the number of returned query is around 20-200. That way innodb doesn't have to compute ...