Map Tile Downloader

The purpose of this module is to download or cache map tiles shown to the user that fall within a specified area (bbox, polygon, wkt) and a designated zoom range.

To use map services (xyz, wms, and wmts), you need to know the URL address of the map service you want to download. The tile URL address contains {s} subdomains, {z} zoom level, {x}, and {y} information, which are always present. While {s} is not mandatory, it has also been included for all scenarios. If {s} is used, don't forget to add subdomains.

After these operations, three different export methods are provided. You should be aware that the hierarchical folder and file structure of the downloaded tiles is in the format zoom_levels/{z}/{x}/{y}. Apart from this, you can download them to the path you define on your server or computer in zip or folder structure, or if you are going to use them within an API, you can access them as a Zip Buffer Array.

Let's illustrate these operations with a few examples..

Installation

intall npm package
``javascript
npm install map-tile-downloader
`

Tile Options

You can use 3 different service for tile URL, This sample for XYZ Tiles
`javascript
// type can be url, wms, wmts
// subdomians sometimes can be -> ['a','b','c','d']
// min max zoom range is 0 to 22
// format can be png, gif, pbf, jpg, jpeg

var tileOptions = {
type: 'url',
url: 'https://server{s}.service-domain.com/abcd/{z}/{x}/{y}.png',
subdomains: [0, 1, 2, 3],
minZoom: 0,
maxZoom: 15,
format: 'png'
};
`


Downloading Area Options

You can use 3 different geometry type for filtering area

$3

`javascript
// Area Sample 1 - GeoJSON - Polygon

var areaOptions = {
type: 'geojson',
data: {
type: "Feature",
properties: {},
geometry: {
type: "Polygon",
coordinates: [
[
[27.12637, 38.42191],
[27.15161, 38.42013],
[27.16448, 38.44603],
[27.14505, 38.44900],
[27.12637, 38.42712],
[27.12402, 38.42284],
[27.12637, 38.42191]
]
]
}
}
};
`


$3


`javascript
// Area Sample 1 - BBOX

var areaOptions = {
type: 'bbox',
data: [27.12402, 38.42013, 27.16448, 38.44900]
};
`

$3


`javascript
// Area Sample 1 - WKT Polygon

var areaOptions = {
type: 'wkt',
data: 'POLYGON ((27.126379667467944 38.42191945460772, 27.151617849934297 38.420139862716354, 27.16448932299207 38.44603848581883, 27.145055922492958 38.449003384245714, 27.126379667467944 38.42712615684721, 27.124024103770523 38.422842188698525, 27.126379667467944 38.42191945460772))'
};
`




MapTileDownloader Module Usage


`javascript
var MapTileDownloader = require('map-tile-downloader');

var areaOptions = {
type: 'bbox',
data: [27.12402, 38.42013, 27.16448, 38.44900]
};

var tileOptions = {
type: 'url',
url: 'https://server{s}.service-domain.com/abcd/{z}/{x}/{y}.png',
subdomains: [0, 1, 2, 3],
minZoom: 0,
maxZoom: 15,
format: 'png'
};

var options = {
tile: tileOptions,
area: areaOptions,
};
var downloader = new MapTileDownloader(options);


`

$3


When you use this method, it'll return a zip buffer array in callback parameter. Then you can use it whatever you want.
Generaly this usage best for API respond
`javascript
downloader.getAsZip((zipFile)=>{
//bufferArray
});
`

$3

You can download zip file to any file path in your server or pc.
`javascript
downloader.downloadZipToPath('D:/export.zip',(status)=>{
console.log(status);
},(status)=>{
console.log(Progress: ${status.progress}%);
console.log(Current: ${status.current});
console.log(Total: ${status.total});
console.log(Downloaded Tile: ${JSON.stringify(status.tile)});
console.log(Status: ${status.status});
});
`

$3

When you use this method tiles will download in hierarchical folders step by step
`javascript
downloader.generateToPath('D:',(status)=>{
console.log(status);
},(status)=>{
console.log(Progress: ${status.progress}%);
console.log(Current: ${status.current});
console.log(Total: ${status.total});
console.log(Downloaded Tile: ${JSON.stringify(status.tile)});
console.log(Status: ${status.status});
});
``

Author

Sr. GIS Dev. Ali Kilic | ali.kilic@gislayer.com | https://akilic.com