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

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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
33 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
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1answer
83 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 ...
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0answers
74 views

Learning classical geography - recommended literature et.c

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 ...
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1answer
73 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 ...
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6answers
279 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, ...
5
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1answer
55 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
44 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 ...
5
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1answer
143 views

Is it possible that a good spatial index just cannot be made?

I have about 6 million rows with geography spatial features - they are all 1000 meter radius hexagons all over the US. There are a couple hundred thousand that would have been NULL, which I updated ...
2
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1answer
121 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 ...
2
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2answers
281 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 ...
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1answer
71 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 ...
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3answers
216 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
200 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
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2answers
227 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 ...
3
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1answer
89 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):= ...
3
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0answers
194 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 | ...
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1answer
301 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 ...
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1answer
926 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 : ...
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1answer
225 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 ...
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2answers
414 views

ST_DWithin uses Geometry or Geography type

assuming I use the following query to match the locations to a poi within 10km distance: SELECT poi.poi_id, h.loc_id, (ST_Distance(poi.geom,h.geom)*111.111) as distanceinkm FROM iut_poi_transl AS ...
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1answer
799 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 | ...
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2answers
369 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?
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1answer
136 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 ...
21
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3answers
448 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 ...
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0answers
70 views

Critera for geometry or geography

What criteria do you need to take account to before you choose geometry or geography map? Is there a book or page about it?
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2answers
225 views

Several questions about using spatial data?

If you have spatial data for SQL server, can you use the spatial data (both geometry and geography) in another application for instance ESRI ArcGIS? Is spatial data a standard that every GIS ...
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3answers
418 views

postgis : is the operator <-> works for Geography also?

With recent postgres//postgis version, you can now use the operator <-> to find nearest rows to a point : Indexed Nearest Neighbour Search in PostGIS Correct me if I'm wrong, but according ...
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0answers
1k views

How to project geographic coordinates (lat/long) to a cartesian system (albers equal-area)?

I am using this matlab package http://www2.ocgy.ubc.ca/~rich/map.html#examples to project the latitudes,longitudes of my data to a specific projection. For this particular case I am using albers ...
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0answers
124 views

Graph of a specific area of USA

I am trying to get the network graph of a specific reason of USA. I have got a couple of options. One of them is using osm2po tool to extract the nodes and edge table from the osm map of a specific ...
3
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3answers
4k views

Insert Geography data into SQL Server 2008

Can someone guide me to or give me an example on how would one go about insert/query Geography data in Sql Server 2008 ( Polygon with 4 points and Point in specific) using C# EF or Linq2Sql. I've ...
3
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1answer
1k views

Open Source Tools for Mobile GIS app development?

I want to create a complete Map application with the facilities of edit geometry and attributes of layers. The server and client for the application should be some open source tools. The application ...
2
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2answers
552 views

Geoserver uses geometry, not geography

When using a SQL database as the store, Geoserver requires that the spatial data are stored in a geometry, not geography column. Naturally, as we are dealing with geospatial features and not just ...
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2answers
339 views

merging block group data that uses 2000 geography with 2010 geography

I would like to combine data sets from 2010 which use 2000 geography with 2011 data that use 2010 census geography. The data is from the contiguous US and is either at block or block group level. I am ...
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1answer
2k views

Issue merging multiple polygons using ST_UNION

Totally brand new at using PostGIS, my first post here on GIS. Apologies if the answer to my question is obvious! I've got regional data loaded into a PostGIS table and want to merge regions that ...
9
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2answers
885 views

Storing GML surface in PostGIS

I'm using PostGIS 2.0.0 and would like to store a GML Surface in a way that allows calculating intersections between that surface and various points and lines. In my case, the Surface will have one ...
3
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2answers
292 views

How to recalculate the the length of a geography linestring from nearby geography point in POSTGIS?

I have a geography type linestring *route_geography geography(LineString,4326)*, its a route from point A to point B. Now I have a point C near that line. I want to find the nearest point on that ...
6
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5answers
615 views

Where can I get (USA) county neighbour relationship data?

I need a graph where each node is a US county and each edge represents a border shared between counties. I do not particularly care about the absolute position or shape of each county (though that ...
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1answer
183 views

How to refine queries using GeoNames

The people on this site have been wonderful in helping me query a list of the worlds parks with something like this query: ...
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1answer
135 views

Getting what seems to be incorrect data from GeoNames

I have a hiking website. I am trying to query for parks big and small around the world where people could potentially go walking or hiking. I was trying to use the GeoNames data and was using query ...
5
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2answers
179 views

How to get geographic information for American and world parks and cities?

I am working on building out park data for my web site. My site is about hiking, so I want to get a list of parks and cities in the world. Is that possible? Where can I get/download/see such ...
31
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4answers
5k views

What are the pros and cons of PostGIS geography and geometry types?

My company uses geometry (the_geom) data type for storing geospatial data. I've recently been acquainted to the concept of geography (the_geog) data type which, as I understand it, stores the SRID ...