Supermap worker pro pre-Cache cut graph count Calculation

Today, the customer asked how long the pre-Cache takes to generate multiple images. Last year, the number of cached images was calculated, after a long time, I flipped through the previous records and R & D colleagues' records as follows for future reference.

 

Content to be prepared before calculation:

1. DPI. Generally, the DPI of a common PC is 72-96. In this case, it is considered that the setting of the deskpro pre-cache is not related to the device. Therefore, the custommapratiox and custommapratioy values are calculated directly, DPI = custommapratiox * 25.4 (generally custommapratiox = custommapratioy. For the custommapratiox values, see the deskpro installation directory/bin/Supermap. INI file value ).

2. The map range, that is, the left and right sides and the upper and lower distance. For details, refer to the pre-Cache index range provided by deskpro.

Get the upper and lower distance: 7612.6676397641 meters

Left and right distance: as shown in the following figure, the distance is 8910.4536856326 meters.

3. The image size is generally 256 or 512 pixels.

4. inch = 2.54 cm

5. Earth's equator length = 40073700 meters

6. Scale.

 

The calculation logic is as follows:

1. Calculate the actual geographic distance of each image (512 pixels/DPI) x 2.54 x scale)/100.

2. If the data unit is meter, the distance between the upper and lower sides/the actual geographic distance of each image ---- get the integer and multiply it.

3. If the unit of data is degree, the actual geographic distance (the length of the earth's equator/360) * Up and down (left and right) is considered. The difference between high latitude and low latitude must be considered here, this is an estimation, so we should consider the same for the moment.

Note: As this is a cut graph, you can calculate the number of left and right map slices plus + 1 or + 2.

 

Example:

Changchun map:

Parameter Value: The image size is 512 pixels, up/down (7612.6676397641), left/right (8910.4536856326), the scale is 1000, DPI = 3.5*25.4 = 88.9

 

That is, the number of image blocks with the value of up and down is = 7612.6676397641/(512/88 .9) * 2.54*1000)/100) = 53 + 1

The number of left and right blocks is = 8910.4536856326/(512/88 .9) * 2.54*1000)/100) = 61 + 1

The number of graph blocks is = the number of top blocks * The number of left and right blocks = 54*62 = 3348. You can refer to the computation with javaspro.

 

Map of China:

Parameter Value: The image size is 512 pixels, up/down (49.724654913), left/right (61.5884246827), the scale is 1000000, DPI = 88.9

Geographic length of each degree = 40073700/360

Number of chunks = (40073700/360) * 49.724654913)/(512/88 .9) * 2.54*1000000)/100) = 38 + 1

Number of left and right chunks = (40073700/360) * 61.5884246827)/(512/88 .9) * 2.54*1000000)/100) = 47 + 1

The number of graph blocks is = the number of top blocks * The number of left and right blocks = 48*39 = 1872, as shown in

Summary: The previous rough estimation shows the number of cached chunks on the map. Because the map in Supermap preview pro expresses the map by scale rather than spatial resolution, DPI-related computing is involved, for more information, see Wikipedia.