React native MapView: what is latitudeDelta longitudeDelta

I also came here because I couldn't find any good documentation and Googling didn't help. The following is from my own research:

Only one of either latitudeDelta or longitudeDelta is ever used for calculating the size of the map. It takes the larger of the two according to the following formula and ignores the other. This is done to avoid stretching the map.

1. The map is sized according to the width and height specified in the styles and/or calculated by react-native.
2. The map computes two values, longitudeDelta/width and latitudeDelta/height, compares those 2 computed values, and takes the larger of the two.
3. The map is zoomed according to the value chosen in step 2 and the other value is ignored.
   • If the chosen value is longitudeDelta, then the left edge is longitude - longitudeDelta and the right edge is longitude + longitudeDelta. The top and bottom are whatever values are needed to fill the height without stretching the map.
   • If the chosen value is latitudeDelta, then the bottom edge is latitude - latitudeDelta and the top edge is latitude + latitudeDelta. The left and right are whatever values are needed to fill the width without stretching the map.

Here are some examples:

// this uses latitudeDelta because 0.04/300 > 0.05/600
<MapView
  style={{width: 600, height: 300}}
  region={{
    latitude: 31.776685,
    longitude: 35.234491,
    latitudeDelta: 0.04,
    longitudeDelta: 0.05,
  }}
/>



// this uses longitudeDelta because 0.05/600 > 0/myVar when myVar > 0
<MapView
  style={{width: 600, height: myVar}}
  region={{
    latitude: 40.689220,
    longitude: -74.044502,
    latitudeDelta: 0,
    longitudeDelta: 0.05,
  }}
/>

i found this in apple developer guide

The amount of east-to-west distance (measured in degrees) to display for the map region. The number of kilometers spanned by a longitude range varies based on the current latitude. For example, one degree of longitude spans a distance of approximately 111 kilometers (69 miles) at the equator but shrinks to 0 kilometers at the poles.

😀 there have an issue in GitHub too for that library that have been resolved
https://github.com/react-community/react-native-maps/issues/637

this visual explanation also help stackoverflow.com
in this Wikipedia article it shows how to calculate exact value
https://en.wikipedia.org/wiki/Latitude#Length_of_a_degree_of_latitude