The science that studies the lands, the features, the inhabitants, and the phenomena of the Earth

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18 views

CartoDB geom (coordinates) join: without exact match

Trying to join two datasets (layers) on CartoDB based on their geographical fields (in CartoDB's the_geom created field). However, the basic ST_Intersection function does not work since its tolerance ...
1
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1answer
50 views

PostGIS - st_intersects using polygons that cross antimeridan/equator

New to using PostGIS and have two situations that I'm working with. In the one case, I have a polygon that crossed the antemeridian and was detecting whether a two separate points located within that ...
0
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1answer
45 views

Use QuadTree for better complexity on search features

I want to improve the complexity of search specific feature when using this function : map.forEachFeatureAtPixel(e.pixel, function (feature, layer) { // Do something.. }); The improvment ...
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1answer
32 views

“polygon” on sphere postgis geography

I have a set of points defined by their longitude and latitude, and I would like to check if they lie within a "polygon" on sphere. By polygon on sphere, I mean area in between 4 lines going between 4 ...
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0answers
52 views

Spatial results tab saying:One or more spatial objects were too large to display

I've saved country borders in my sql server 2012 as geography data from geojson files. It turns out that when I query all the boundaries that have an administration level 2, not all the polygons are ...
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2answers
140 views

GeoJson to Spatial Geography in sql server 2012, fix orientation of polygon

I've download from Mapzen many geoJson files related to countries with their respective administration level. Then I've parsed all the geoJson files and saved them to my sql server 2012 as geography ...
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1answer
22 views

Territories that are not connected

I am looking for territories that are divided between two or more countries in a non-contiguous way. E.g, country A receives the western part of the territory, then country B receives a part to its ...
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0answers
44 views

Quantifying amount of sunlight falling in a region

I am trying to objectively quantify or provide some form of indication that could point toward the amount of sunlight Anyone knows if there are any datasets (either instrumental or remotely sensed ...
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1answer
119 views

Is there any online viewer which displays the polygons assuming great circle lines for the edges?

My question is similar to this one: Are there any online WKT editors? The links given in answers have been very useful to me. However, it seems that when the tools in question display maps, they ...
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2answers
289 views

“Official” delineation of North American mountain ranges

I need to subset mosaics of remotely sourced data to the extents of several prominent North American mountain ranges, starting with the Sierra Nevada. After searching for the boundaries of the range ...
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1answer
44 views

Location based service with normal image

We have an image for a park which has been rendered like this: Now we want to add some geographic service based on the data: building an Android Application with the following features: Display ...
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1answer
96 views

ArcPad custom edit form validation behaviour

I have a custom ArcPad form, which includes the geography tab. Users use this tab to update coordinates using the GPS. When user press OK in the edit form, I want to first check that they have not ...
0
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1answer
93 views

LiDAR data for Palawan (Philippines)

Is there any public or private sources of LIDAR data for San Paul river in Palawan (Philippines)? Searching online has not lead me to any sources, and I am unsure how the commercial world of LIDAR ...
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2answers
1k views

Order sql server spatial geometry distance by the nearest

I have a geometry column in a table, I want to get the N nearest neighbours; here is a specific example with the geography type DECLARE @PTO Geography = Geography::STPointFromText('POINT(-57.432546 ...
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1answer
2k views

Choosing SRID and what is its meaning? [closed]

I'm new to GIS, in PostGIS, and I'm struggling with the SRID concept. How do you choose a SRID for a database column? This is making me crazy. Why do I need to choose a SRID? What's its meaning? ...
2
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0answers
74 views

Needing to find parent zip code of a bunch of missing zip codes in the US

We're using MapPoint to export zip code / territory combinations. Unfortunately, the export doesn't include PO Box zip codes which mean that we're missing a lot of zip codes The PO Box zip codes are ...
3
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1answer
81 views

GIS through Games: Ideas or Links [closed]

I'm managing a project - http://nepanode.anl.gov aimed at improving data awareness and sharing around Environmental impact analysis. I'm struggling to come up with ways to engage users and show them ...
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2answers
5k views

Equations to convert from global cartesian coordinates to geographic coordinates

First, I needed to convert geographic coordinates (like those received from GPS) to global cartesian coordinates. I found an earlier question (How do I calculate a xyz-position of a gps-position ...
2
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2answers
810 views

Maximizing Code Performance for Shapely

I've written this code in order to calculate the percent cover of grassland within a national park, within 20km^2 of points of recorded occurrences for a species. It is designed to only consider the ...
2
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1answer
971 views

PostGIS get geometries within a radius of n meters using WGS84 [duplicate]

select * from zones z where st_intersects(z.geom, st_Buffer(ST_SetSRID(ST_Point(2.336031, 48.863172), 3857),1)); It looks like the 1 in the st_buffer is being interpreted as degrees, I need to find ...
9
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2answers
1k views

why do people use geometry to represent geography?

Historically I've mainly worked with simple latitude and longitude coordinates in a SQL Server. I stored them as a geography datatype in SQL Server, and rendered them on a variety of displays ...
2
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1answer
3k views

Geometry datatype to latitude /Longitude MS SQL Server

I need to convert Sql Server geometry datatype to latitude /Longitude I have just imported a shapefile to my table (geometry) This query does not work:- select geom.Lat as [Latitude], ...
2
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0answers
29 views

Characterizing territory according to its relief using ArcGIS Desktop?

I want to characterize the territory according to its relief with ArcGis 10. I'm trying to define a wide territory by its relief, but I would like to do it in an automatic or semiautomatic form with ...
2
votes
2answers
154 views

Buffering points bounded within polygons

I've checked around and didn't see this one yet, hoping somebody can help me out (preferably without code, but I'm all ears). I'm using arcGIS 10.1 on an i5 win7 machine with 16g RAM. Not a xeon but ...
0
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1answer
380 views

The ratio Pixel distance to geographical distance?

I have had this problem for several days and I have no idea to solve it. The problem is that I am trying to find out the length and width of ships from a Bing map. I got the location point (lon, ...
1
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1answer
65 views

What is the radius of earth [duplicate]

What is the real radius of earth? Google says 6378.1 km Wiki says 6371 km And there are references for 6378.7 km I'm using maximum radius 6378.7 km in distance calculation in spherical law of ...
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3answers
170 views

Equal Area Projection for Central Ethiopia (37N)

Can anybody please tell me what is the best equal area projection for central highlands of Ethiopia. I am assuming Albers Equal Area Projection. Any suggestions?
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0answers
36 views

Calculate end point Height above the MSL of the target point given a starting point, distance, azimuth and elevation [duplicate]

We need to find the end point height (from the earth surface) given the start point lat, lon, azimuth (270 deg), distance (500 km) and elevation above the horizon of start point (10 deg). The ...
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1answer
42 views

Postgis add Geography to function()?

i was wondering im getting different results when using geography() on different positions within a query. So, whats the most accurate way of forcing geography() over a functions with geometry ...
2
votes
1answer
594 views

POSTGIS: function st_collect(geography) does not exist

I am trying to use some Geography functions, but I am getting an error that (all) functions are not existing. I have checked other Stackexchange posts (e.g. this one), but the solutions did not work ...
2
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1answer
133 views

Learning classical geography - recommended literature etc

I've been working in the field of GIS for a few years now, and there are some disciplines of knowledge where I lack a good degree of education. My educational background is that I've studied computer ...
1
vote
1answer
640 views

PostGIS convert GeoJSON to geography

While there are functions to convert geography to GeoJSON: text ST_AsGeoJSON(geography geog, integer maxdecimaldigits=15, integer options=0); I do not see any way to go the opposite direction ...
8
votes
6answers
778 views

What is the easternmost point in the US?

In his blog for The Atlantic magazine, James Fallows claimed that Eastport, ME was the easternmost point in the US. A writer commented that no, the easternmost point in the US was somewhere in Alaska, ...
6
votes
2answers
323 views

Min. weighted average distance from multiple points

I am a complete beginner in mapping-related topics. Still, I´ve been wondering if anyone know this problem. It might be well known, I just don´t know its name. Initial situation: nx : x geographical ...
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1answer
51 views

Countries with a small number of sides

Please accept my appologies if this question is off-topic here; this is the closest match to the topic of my question. I am looking for countries and states whose map is a polygon with a small number ...
3
votes
1answer
352 views

GeoDjango: read geometry column in geography field

I have a Django application that needs to work with an existent PostGIS database, apart from its own database. I've configured multidatabase support, created a database router, created models for the ...
5
votes
3answers
6k views

What's the fastest way to do a bounding box query in PostGIS

I have a Postgres table, with almost 2 million rows, with a long-lat coordinates field in the form POINT(-73.4938 33.2405). Supposing there's a geospatial index on that field, what's the most ...
0
votes
1answer
161 views

Convert an area to meters² in PostGIS

I have this query : SELECT ST_AREA(geom::geography) FROM region The (geom) contains polygons from a shapefile imported into PostGIS with shp2pgsql. I've appended ::geography, else the result of ...
9
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3answers
443 views

Where can I publish my paper for free?

Is there any magazine (or some other such place) where university students can publish a GIS/Geo related article freely (in English or French)?
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1answer
676 views

Maximum size on the bounding box with ST_MakeEnvelope and && and geography column in PostGIS?

I've done quite a few google searches, but haven't managed to find anything that has helped me directly. I've got a few features in a PostGIS table with a geography column. The features are focused ...
2
votes
2answers
2k views

Shapefiles for US city and Zip level

I already have the information for US states and Counties. I have the information in the Json files. I want the information for ALL US city and Zip Code information. Any leads appreciated. I cant ...
4
votes
1answer
161 views

Postgis 2.0 geographic polygon has max longitudinal range

My problem is that I have a load of geographic point data (srid 4326) in a table. A user may do a bounding box search - essentially create a polygon as follows: l_poly geography(Polygon,4326):= ...
5
votes
0answers
552 views

Finding poi using st_dwithin in postgis

I am not familiar with gis or writing sql, so my understanding in this field is lacking. I have a hundreds of lat/lng geographic coordinates stored in a single table called Places like this: ID | ...
1
vote
1answer
741 views

SQL 2012 - How can I convert MultiLineString to Geography?

I have a Geometry LineString that I wish to convert to Geography. Since the Geometry isn't valid , When I use MakeValid on it, SQL convert it to MultiLineString and than the Geography creation is ...
2
votes
1answer
5k views

Trying to convert geometry to geography keep failing in MSSQL 2012

In MSSQL I have LineString in Geometry type. When I try to convert it to geography using : ...
4
votes
1answer
852 views

For which operations a PostGIS Geography index is useful?

I need to do KNN- and within-region queries for POI data. I store the POI locations in a geography column. Since I understand that ST_DISTANCE doesn't use the geography index, I added a geometry index ...
1
vote
1answer
2k views

Distance between DB field and Point using PostGIS

I'm using Postgresql 9.0 with PostGIS 2.0 extension. I've got the table and geographic field location: =# SELECT * FROM geography_columns; f_table_catalog | f_table_schema | f_table_name | ...
4
votes
2answers
3k views

At the northpole, which way is east? [duplicate]

If a person stands on the north, or south pole. How do they determine which way is east/west?
2
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1answer
202 views

I would like to know about Careers in GIS [duplicate]

I am currently doing my MS software engineering. I am very much interested in GIS. I would like to know about the various opportunities available in this field and also the skills that i will have to ...
24
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3answers
629 views

Are ellipsoids a mathematical necessity?

The literature usually just tells us that the Geoid is complex to describe mathematically and that we therefore fit different Ellipsoids to approximate it. Are these Ellipsoids mathematically ...