This is what people commonly refer to as a "projection". This can include things like Robinson , Albers Equal Area , and one of my personal favorites Waterman butterfly. These are different parts and are made up of different pieces, but both of these together create a coordinate system. This is the very simple definition of both, but if you want to get into the math of everything, ESRI has good documentation in their resources section discussing map projections.
Wikipedia's page on map projections also does a very good job of explaining the different types of PCSs, what distortions are caused, etc. Many projections also have their own pages explaining their history, math, etc. World projected with this projection looks like this:. Sign up to join this community. The best answers are voted up and rise to the top. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Learn more. Modified on: Tue, 27 Nov, at PM.
Actually, WGS84 stands for World Geodetic System and comprises of four different things: an ellipsoid a horizontal datum a vertical datum a coordinate system An ellipsoid The shape of our earth is not perfectly spherical.
A horizontal datum When you position the ellipsoid on a certain location with respect to the earth, on the so-called anchor point, you set a horizontal datum.
A vertical datum When you determine the elevation of your position you can measure that elevation with respect to the WGS84 ellipsoid. A coordinate system WGS84 can also be one type of geographic coordinate system. Plotting WGS84 on a map When you plot the geographic coordinates on a two-dimensional map you apply a map projection.
Yes No Send feedback Sorry we couldn't be helpful. Help us improve this article with your feedback. Related Articles. Your email address will not be published.
Skip to content. Geodesists believe the error is less than 2 centimeters which is better than NAD Leave a Reply Cancel reply Your email address will not be published. Toggle Menu Close. Search for: Search. You'll adjust the parameters for this projected coordinate system to center it on the chosen location, instead of true north. It is also listed in the Custom category of available coordinate systems. Coordinate systems in the Custom category are not saved.
Next, you'll add it to a favorites folder so you can use it in future maps. Favorite coordinate systems are stored as. The map redraws with the new projected coordinate system. It looks similar to before, but the center of the map if not the basemap has shifted. Both geodesic and planar measurements from the new point will now be accurate. In ArcGIS, you can choose between planar or geodesic measurements. But your map reader will not have this choice; they will only see a flat map on a screen or piece of paper.
An equidistant projection is the right choice for this map to allow everyone to assess distance correctly from the north pole. Sometimes, you won't find a projected coordinate system that is ready-made for your map's purpose. ArcGIS Pro allows you to modify any coordinate system to have parameters that better suit your needs. Next, you'll learn how to create a custom projected coordinate system using suggested parameters from ArcGIS Pro.
The map you'll make next is narrow enough but doesn't fit properly into an existing UTM zone. In this lesson module, you'll learn how to find the correct UTM projected coordinate system for an area of interest, and how to create a custom projected coordinate system to use when a standard UTM zone doesn't fit.
You want to map the border between Finland and Russia. This will be a reference map, meant to give descriptive context to the border region.
You want to use a conformal projection to show the shapes of features in their most recognizable forms. This map currently uses the Web Mercator projection.
In addition, this projection distorts area and distances dramatically in higher latitudes. The white rectangle represents the area you want to map. UTM projected coordinate systems are conformal and their distortion of other map properties is minimal. UTM divides the earth into 60 zones. Next, you'll use a spatial filter to determine which UTM zone to use for your map.
The values under Selected extent update to match the extent of the Map Neatline layer. The XY Coordinate Systems Available list is filtered to only contain coordinate systems with extents that overlap with your map.
There are two UTM zones for the area that you want to map, 35N and 36N, and you can't tell from this list which zone is best. Next, you'll add a layer to your map to visualize the UTM grid. UTM projected coordinate systems minimize distortion to reasonable levels, but only within their zone areas.
Neither zone 35 nor 36 will provide this benefit for your map area. Next, you'll create one for this region. ArcGIS Pro can suggest new custom projected coordinate systems based on two criteria: distortion property and map extent.
The parameters of the new custom projected coordinate system appear in the Result box. Transverse Mercator is a common projection, used by the UTM coordinate systems and some State Plate coordinate systems.
Transverse Mercator NGA is a variant of this projection, with the added advantage of being able to show a larger portion of the world. The False Easting shifts the origin point of the coordinate system far away from your map area to ensure that no coordinates have negative values. The new projected coordinate system distorts shapes that are far from its central meridian The image below shows a comparison of the map in the new custom projected coordinate system and in Web Mercator.
In the custom coordinate system, the shape of the neatline polygon is a trapezoid instead of a rectangle. Its northern edge is shorter than its southern edge. The rectangle in Web Mercator is misleading: on the earth, these lines are not the same length. The new projection represents them more accurately. The two maps shown above are drawn at the same scale: 1 to 20 million. But that scale is meaningless in the Web Mercator map, since its area distortions are so extreme.
Distortion in the Transverse Mercator map is small enough to be unnoticeable, and more precise measurements can be made on that map. Earlier in this lesson, you learned how to modify coordinate systems. How could you modify the Equal Earth projection from the start of this lesson to better show the Pacific Ocean? Change the central meridian to Copy and modify the Equal Earth world coordinate system. In this lesson, you learned some techniques and explored resources that will help you choose an appropriate map projection:.
Take a closer look at the maps you see on the internet, in the news, or in apps. Do they use a projection that is well suited to their purpose?
0コメント