(Android map development) 4. Map offset Solution

1Source of map offset problem:

For security reasons, in order not to expose the geographic information of important locations, all electronic map service providers need to add offsets and encryption to map data, so we are using google, when you map an electronic map service provider such as baidu, you will find that the location displayed on the map is different from the actual location.

2Special Phenomenon of map offset:

2.1The map in Beijing has no offset. Why?

Beijing, as the geographic origin of a map in China, can understand that there is no offset problem.

2.2Whether the actual offset is in a certain geographic range and changes dramatically

The actual offset is within a specific geographic range, and the changes are almost fixed,

Cause: In fact, if the offset changes sharply within a local range, you can go straight on the street, and the map shows you are flying randomly, this will not happen (from this perspective, it is possible to correct the human offset)

2.3Whether the satellite chart has an offset problem

The satellite map has no offset problem, and the satellite map is not in the map category.

3. Several offset policies:

3.1 obtain the support of the map service provider and get the offset algorithm

Currently, Baidu and google's major customers who pay the map usage fee on a yearly basis can directly obtain the offset algorithm.

Baidu needs million yuan a year for google.

(If you have a rich business project, this stuff is good)

3.2 enter the latitude and longitude through the offset interface of the Internet to obtain the offset

Advantage: improved positioning accuracy and low cost

Disadvantage: Timely Interconnection

3.3 map service is implemented through the APIs of third-party map service providers (the feedback map has no offset problem, and small companies are not subject to human management)

Advantage: the offset problem is directly solved.

Disadvantage: the quality of third-party interfaces and maps is not good.

3.4 manually correct the offset

Principle:

1) define a region (such as Guangzhou ,)

2) divide the map by longitude and latitude, and divide the Guangzhou area into other large regions (the more accurate and finer the map is based on actual business needs)

3) then, randomly calculate the latitude and longitude offset for this region and take an average value,

4) locate the map to obtain the current latitude and longitude, and find the offset of the corresponding region,

5) Merge the offset and display the map

Advantages: Convenient and supports mainstream map suppliers

Disadvantages: Only small-scale correction is supported. If a large-Range correction is performed, the verification data packet is too large.

(Self-implemented This is)

Special thanks:Zhuoyi review network(New places to release Android applications)Sponsorship support !!!