Saturday, July 28, 2018

How to Extract Accurate Point Coordinates and Heights from Google Earth

In this post, we will use free software to extract height/elevation/altitude of points above sea level for any location in the world from DEM (digital elevation model) databases. This is fairly good data for drawing contour maps, draw a profile of a track or to colorize points by height above sea level.

The sources of the elevation data is from a DEM (digital elevation model) databases as explained below:-

DEM data sources
USGS: NED The U.S. Geological Survey's excellent National Elevation Dataset covers the United States, Canada, and Mexico. 1 arc-second (~30-meter) horizontal resolution is available in most areas (NED1). For Alaska, 60-meter data is also available (NED2). 
NASA: SRTM1 NASA's SRTM1 database (from the Space Shuttle Radar Topography Mission) has a resolution of about 30 meters. Previously, SRTM1 data was only available for the United States (and was not very useful because NED1 is generally better), but recently NASA has released SRTM1 tiles for the entire world. GPS Visualizer's server does not contain the full global dataset, but it does contain all of Europe, Japan, South Korea, and Taiwan, as well as parts of Australia, New Zealand, and South Africa. Additional locations will be installed upon request. 
ASTER: The ASTER GDEM is a joint product of NASA and the Japanese Ministry of Economy, Trade, and Industry (METI). ASTER has very good 30-meter coverage of the entire world, but the awkward download process and the massive size of the database make it impractical to store all of it on ASTER files for Iceland are available, however, since none of the other 30-meter databases cover that area. (As with SRTM1 data, additional files can be added upon request.) 
NASA: SRTM3 NASA's SRTM3 dataset includes 90-meter resolution for the entire world.

Monday, July 23, 2018

GIS Base map with Web Map Service (WMS)

Web Map Service (WMS) is a convenient way for an organization to publish or share spatial datasets online that can be readily used in GIS. WMS is a popular standard for publishing maps on the internet.

WMS is hosted on a remote server. Similar to a website, you can access it as long as you have a connection to the server. WMS is a standard protocol that serves geo-referenced map images using data from a GIS database.

With WMS you have access to a live service that will automatically refresh its view if you pan or zoom on the map. So, you always have access to the latest and upto date published data.

WMS are perfectly use as background maps for GIS project. It can be used on web, mobile and desktop GIS applications. All you need is the WMS getURL (GetMap or GetCapabilities) from any of the organizations that publish or share spatial datasets online.

Some WMS organizations are:-
1~ USGS:
2~ Boundless Geo:
3~ Mundialis:
4~ Terrestris:
5~ Geofabrik:
6~ The Hug:
7~ Omniscale:
8~ WhereGroup:
9~ Sinica:

Friday, July 20, 2018

Difference between GeoJSON and TopoJSON

In the Geospatial industry, data handling and conversion is a vital skill especially when data are been moved from on platform to another.

Some data formats work better on one platform than another. For example, data in shapefile format are more flexible on desktop apps than on web apps. If you are looking for an excellent data format to use on the web, then "GeoJSON and TopoJSON" data formats are your best option. But what is the difference between "GeoJSON and TopoJSON"?

In this post, I will attempt to differentiate the two powerful web based geospatial data formats (GeoJSON and TopoJSON).

GeoJSON is an open standard format designed for representing simple geographical features, along with their non-spatial attributes. Both GeoJSON and TopoJSON are based on JSON, the JavaScript Object Notation.

As extracts from Noah Veltman of and Mike Bostock (and other contributors to the TopoJSON extension) repectively:-

GeoJSON and TopoJSON are two web-friendly file formats for geographic data.
A GeoJSON file is a text file with a list of features and, for each one, a bunch of latitudes and longitudes describing its geometry.
A TopoJSON file is similar, but instead of storing the latitudes and longitudes directly, it describes the topology (geometrical properties and spatial relations of figures) of a group of features, meaning the borders between them. TopoJSON files are usually much smaller, but require a little bit of extra processing in the browser when you want to display one on a map, and can potentially lose details from the original latitudes/longitudes.

TopoJSON is an extension of GeoJSON that encodes topology. Rather than representing geometries discretely, geometries in TopoJSON files are stitched together from shared line segments called arcs. TopoJSON eliminates redundancy, offering much more compact representations of geometry than with GeoJSON; typical TopoJSON files are 80% smaller than their GeoJSON equivalents. In addition, TopoJSON facilitates applications that use topology, such as topology-preserving shape simplification, automatic map coloring, and cartograms.

The advantage of TopoJSON over GeoJSON is size and encoding of topology. So, if the file size or topology of feature is paramount to you, use TopoJSON instead of GeoJSON.

Monday, July 16, 2018

Map of 2018 Ekiti State Gubernatorial Election Final Result

The much anticipated 2018 Ekiti state gubernatorial election has come to pass and 24 hours after the result has been announced by INEC, Nigeria social and news medias are flooded with the result.

Unfortunately, non has analysed the result on a map. In this post, I will related the result to map of Ekiti state so we can see the spatial relationship in the result.

Ekiti state has 16 local governments and 177 electoral wards.

Thursday, July 12, 2018

Geo-visualization of FIFA 2018 World Cup

As stated on Wikipedia page: The 2018 FIFA World Cup is the 21st FIFA World Cup, a quadrennial international football tournament contested by the men's national teams of the member associations of FIFA. It is currently ongoing in Russia starting from 14 June and will end with the final match on 15 July 2018.

In this post, I will attempt to visualize the participants on a world map starting from qualifying countries, group stage, round of 16, quarter finals, semi finals etc.

Let's get started....

Saturday, July 7, 2018

Python and Data Science Blogs

The list below are some of my favorite blogs I have followed and gained alot of from over the years. I hope you will also like them.

Some useful blogs for python and data science enthusiasts:-
















Wednesday, July 4, 2018

Geo-spatial Professional Areas of Interests

The Geospatial industry is quite a vast industry that encompasses many areas of interest. In this article, I will briefly take a look at the most common areas.

As someone who works in the Geospatial industry, you will find yourself doing one or more combinations of this areas of interests:-