How is the Mercator projection used in navigation?

How is the Mercator projection used in navigation?

WGS 1984 Web Mercator and WGS 1984 Web Mercator (Auxiliary Sphere) use a conformal projection that preserves direction and the shape of data but distorts distance and area. Published in 1569 by Gerardus Mercator, the Mercator projection was created for use in navigation.

How are continents shown on a WGS 1984 map?

The maps display the continents plus a 15×15 degree graticule that covers the entire surface of the earth. 1) WGS 1984: The 15×15 degree graticule cells appear as squares. The map uses a modified Plate Carree projection to display the latitude and longitude values.

How does the plate Carree projection work on a map?

The map uses a modified Plate Carree projection to display the latitude and longitude values. Note that distances are very distorted in the east-west direction, north or south of the Equator. In this coordinate system, the North and South Poles appear as lines as long as the Equator.

How to measure distances using ArcGIS Online Mercator?

To understand the discrepancies in measurements returned by the default ArcGIS Online Mercator and a more local coordinate system, take a look at this example application, which is zoomed into the town of McMinnville in northwestern Oregon.

Is it safe to measure polylines in Web Mercator?

If you use the new ArcGIS Online services, avoid the temptation to perform measurements of polylines and polygons in Web Mercator. You should instead re-project user-submitted geometries into a more appropriate coordinate system before you perform a measurement.

Is the Mercator projection strictly ellipsoidal or spherical?

The projection is neither strictly ellipsoidal nor strictly spherical. EPSG’s definition says the projection “uses spherical development of ellipsoidal coordinates”. The underlying geographic coordinates are defined using the WGS84 ellipsoidal model of the Earth’s surface, but are projected as if defined on a sphere.

What happens when you delete a field in a shapefile?

The ‘Deletion Flag’ as set in the Shapefile standard will be passed over (the tuple in the if statement), and we want data from the lists that follow the tuple that define the field name, data type and field length. Basically we are simply replicating the field structure from the original into the new.

How to reproject a shapefile using pyproj?

In this post I will use the PyShp library along with the PyProj library to reproject the local authority boundarie s of Ireland, in Shapefile format, from Irish Transverse Mercator to WGS 84 using Python. To follow along download the admin boundaries from the Central Statistics Office (CSO) and rename the files to Ireland_LA.

How to save and run a polygon shapefile?

Save and run the file. Open the Shapefile in a GIS to inspect. Have a look at the attribute table, nicely populated with the data. You should be able to configure the code for other polygon files, just change the original input Shapefile, set the projections (input and output), and save a new Shapefile.

When did Web Mercator become the de facto standard?

WGS84 is often described in Web Mercator, a variant of the Mercator Projection, and became the de facto standard for web mapping when it rose to prominence following Google Maps adopting it in 2005. It is used by virtually all major online map providers such as Google, Bing Maps, OpenStreetMap, Mapquest and ESRI.

When did the Web Mercator dilemma come about?

The so-called ‘Web Mercator Dilemma’ is the result of activities and decisions that date back to the late 1980s.

How did James Talmage come up with the Mercator map?

He found that he was able to fit the United States, India and much of Europe inside the outline of the African continent. Inspired by Krause’s map, James Talmage, and Damon Maneice, two computer developers based out of Detroit, created an interactive graphic that really puts the distortion caused by the Mercator map into perspective.