Configure Google Maps map projection in Supermap Desktop

Let's take a look at the map projection used by Google Maps.

Google Maps,Virtual EarthMap projection used by network geography is often calledWeb MercatorOrSpherical MercatorThe main difference between it and conventional mocato projection is thatSimulate the Earth as a sphere rather than an elliptical body. For more information about why projection is required, see liongg'sWhy map projection

Why is it a Circular Sphere instead of an elliptical sphere?

This is simple because it is easy to implement and easy to calculate. The accuracy is less than 0.33% in theory, especially when the scale is larger and the terrain is more detailed.Google Maps uses the reference sphere of WGS 84..

WebMocato projection Coordinate System:

Take the whole world, the Equator as the standard weft, the primary meridian as the central meridian, the intersection of the two is the coordinate origin, east to north is positive, and west to south is negative.

X axis: Because the equator radius is 6378137 meters, the Equator perimeter is 2 * pI * r = 2*20037508.3427892. Therefore, the value range of the X axis is as follows:

[-20037508.3427892, 20037508.3427892].

Y axis: It can be seen from the mocato projection formula, but also has a signal, when the latitude Phi is close to the pole, that is, 90 °, the Y value tends to be infinite. This is the "lazy engineer" who limits the value range of the Y axis

Create a square between [-20037508.3427892, 20037508.3427892.

As we all know, we cut static images in advance to improve access efficiency. I just tell you why it is like this. Therefore, the range in the projection coordinate system (meters) is: Minimum (-20037508.3427892,-20037508.3427892) to maximum (20037508.3427892, 20037508.3427892 ).

[Note: The above section is taken from liongg'sFull resolution of Google Maps map projection (1): Web mocato projection]

I think this section has been clearly written, so we need to know two points:Google maps is a mocato projection, and the Earth is simulated as a sphere rather than an elliptical body..

Note the above 2.1, which is also the focus of our Configuration:

First, we will set the sphere for the data source. here we need to modify the projection method of the data source. The configuration is as follows:

On the data source to be modified, right-click and select "properties", for example:

Here we use the reference elliptical body wgs_1984, but here there is an "elliptical flat rate" of 0.0033528107, and Google Maps is a sphere, therefore, we need to set the "elliptical flat rate" to 0, so we need to "reset the projection ":

Select the latitude and longitude coordinate system, but select "user define" in the "geographical coordinate system", and then click Next:

Please refer to the above value for settings, mainly set "equator radius" to: 6378137, "flat rate" to: 0, after the completion of the effect is as follows:

In this case, the data source projection settings are complete. Close this window.

Next, we need to set the map projection, right-click the map, and select "attribute ":

The projection method we selected here is Mercator, but there is also an "elliptical flat rate", which is not what we want, so click "set ":

Please refer to the settings, and then "Next ":

Please refer to the settings, and then "Next ":

Here we set the proportional factor to: 1, and then "Next ":

In this way, the settings are complete. Click "application" and you will be OK!

After the above configuration, we have completed the setting of the same map projection for Google Maps in Supermap desktop. Some may ask, what is the purpose of this setting?

This depends on the application of each person. In this way, I set the projection and coordinates to be the same as those of Google Maps, which can be used for graph cutting, generate the same image data as Google Maps.

I will leave it blank when using the cut graph.ArticleFor more information, see.

Due to the limited level, it is inevitable that there will be errors in this article. I hope my friends can correct me.