The relationship between 1 degrees and 1 meters in a geographic coordinate system

Problem Description:

Get a vector file of the road data, the coordinate system is gcs_wgs_1984,

Its prj file is:

geogcs["gcs_wgs_1984",

datum["d_wgs_1984", spheroid["wgs_1984", 6378137.0,298.257223563]],

primem["Greenwich", 0.0],

unit["degree", 0.0174532925199433]

]

What is shown in ArcGIS catalog is:

Angular Unit:degree (0.017453292519943299)
Prime Meridian:greenwich (0.000000000000000000)
datum:d_wgs_1984
spheroid:wgs_1984
Semimajor axis:6378137.000000000000000000
Semiminor axis:6356752.314245179300000000
Inverse flattening:298.257223563000030000

The purpose is to:

According to the range of the road layer, the 4km*4km grid is divided to facilitate the subsequent processing;

Analysis:

Because the geographic coordinate system shows the degree of minutes and seconds, so in order to divide the KM grid, you need to know in the gcs_wgs_1984 coordinate system, 1 meters corresponding to the number of degrees?

Then use the Fishnet tool in the toolbox;

Baidu Results:

Http://www.08kan.com/gwk/MzA5NjE1OTM4OA/202219029/1/510f7a9843264a7a5e45a7bc411412d9.html

Ask:
What I read in a book is that in the wgs_1984 coordinate system using decimal degrees, the data accuracy is 1 cm and the tolerance value is (0.01/(6378137*0.017453292519943299))/ 10, approximately equal to 8.983e-9, at that time did not understand why to divide by (6378137*0.017453292519943299) This string of numbers, now also do not understand, I now the data of projected CoordinateSystem is Wgs_ 1984_UTM_ZONE_49N, in accordance with this topology, the topological tolerance value by default is 0.001, not 8.983e-9, I do not know why, if I change 0.001 to 8.983e-9, at the end of the error, I do not know why, please advise.
For:
Dividing by that number is a circular arc that calculates the amount of 1 meters on the equator. 360°=2π* Equatorial radius (≈6378137) meters, then 1 meters ≈360°/(2π*6378137), and 2π/360≈0.017453292519943299, which is 1 meters ≈1/(6378137* 0.017453292519943299) ° and is generally set to a tolerance of 10 times times the accuracy. According to the above analysis it is not difficult to draw that result.
The unit of wgs_1984_utm_zone_49n is the meter, so it should be set to 0.001 instead of set to 8.983e-9, only a geographic coordinate system in degrees can be set to 8.983e-9

The above analysis indicates that:

At the equator 1 meters equivalent degree: 1 meters ≈1/(6378137*0.017453292519943299) °

1-kilometer =4000*1/(6378137*0.017453292519943299) °=0.03593261136478085740510005025863

So:

The interface in ArcGIS is as follows:

The result is basically satisfactory, why do you say so?

Because the resulting side length is approximately equal to 4000 meters, and the length and width are different, this may be due to the deformation of the cause!

Other methods:

You can project the data and do it again!

The relationship between 1 degrees and 1 meters in a geographic coordinate system