(iv) offline map of the URL of a variety of tiles by Webgis in the column number

1. Preface

In front of me, I spent two pages explaining how to get the line number, and explain why we have to get the number of rows. In this chapter, I'll list some of the common URL styles for requesting tiles, and give a general explanation.

I am here to divide the map into offline maps and online maps. The so-called offline map, which is a map saved locally and not published. Online maps are published with online maps that can be accessed through a browser.

2.ArcGIS Tangent--exploded Type

In the previous section I have posted the exploded type of transduction picture, here again.

So how to calculate the URL of this tile by the row number. We can begin by observing three conclusions:

(1) L The representative of the beginning of the level,r represented the Row,c beginning of the representative of Col.

(2) After determining this, we continue to observe, you can find that the number after the L is a two-bit string, R is a eight-bit string, after C is also a eight-bit string.

(3) The number after the English is 16 decimal, then the amount of the less than 0 supplement.

I think you know these three conclusions, through the line number to obtain the address of the offline loose tile is not difficult, we only need to convert the level, row number into 16, the number of less than 0 complement, and finally with the English logo, so the address of the tile can be found.

3.ArcGIS Tangent--bundle Type

Here I also first put out this type of tile style:

The tile's acquisition is really out of the picture, because this compact format of ArcGIS wraps the image and doesn't visually look at it. ArcGIS claims that this format is currently not a public parsing method, and it is also difficult to receive the corresponding parsing method on the Internet. However, one of my very thought colleagues took some time last year to crack the tile acquisition method in this format and we have successfully applied it to multiple projects.

Here I just give a few hints, according to my tips, I think the reader as long as a little more strength must be able to crack:

(1) Similarly, L, R, C is the map level, line number, column number.

(2) The string fixed after R and C is 4 bits.

(3) The number after R and C is converted to 16 by dividing the row number by 128, then the insufficient number of digits is 0.

(4) The bundle file is stored in the picture binary stream, the Bundlex file is stored in the corresponding tile in the bundle address, is an index file.

(5) then .....

Then it is how to find where to read in the index file, get the tiles in the bundle where the address, and then go to the corresponding address in the bundle to read the image. However, it is added here that the bundle is not only tiled, it also contains the size of each tile, that is, how many binary numbers you need to read this tile.

Thanks again for the crystallization of my colleague's wisdom, otherwise this article must be incomplete.

4. Tile format--Tile of land Bureau

In our project, we can often see non-ArcGIS Tile series, such as the Super map, the middle ground and so on. Here I give a land bureau of the tile format, in fact, many of the land Bureau's own tiles are the format of this organization.

I will also give the tile style diagram first:

Everybody is not very strange, obviously should be three levels of Ah, level, Row, col of Ah, how this has four levels. Yes, the Land Bureau's tiles, in addition to these three parameters, there is a Fileid parameter.

Here I directly give the conversion formula:

Fixedlevel=level;

Fixedrow=math.floor (ROW/4);

Fixedcol=math.floor (COL/4);

Fileid= (Row)%4) + (Col)%4);

The address of its URL is \fixedlevel\fixedrow\fixedcol\fileid.png.

5. Summary

In this section we analyze two common offline map formats and a special offline map format. From this analysis we can see that no matter what the map, the determinant is a necessary condition. So how to get the line number is not very clear reader, please put my second and third section of this series again attentively read again, I believe you and I must have a different harvest.

In the next section, we will explain the URL parsing of the online map, and the URL of the online map is relatively simple. We also analyze online maps that conform to OGC standards and special online map services. Welcome to the continuous attention.

When we start to wake up early in the morning, or when we're not asleep at midnight, it means we're getting mature.

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