# 第三方数据与代码

## 地形数据

- 数据集：Terrain Tiles，由 Mapzen（Linux Foundation 项目）托管在 AWS Open Data
- 注册页：https://registry.opendata.aws/terrain-tiles/
- 瓦片：https://s3.amazonaws.com/elevation-tiles-prod/terrarium/{z}/{x}/{y}.png
- 署名与许可说明：https://github.com/tilezen/joerd/blob/master/docs/attribution.md

本页使用青海省阿尼玛卿一带 z=12 的 72 块瓦片，裁切为 40.2 × 35.4 km，重采样为 512 × 512。该区域主要涉及全球 SRTM / GMTED2010 / ETOPO1 数据。

按 Mapzen 托管服务的要求，附完整署名：

```
* Mapzen
* ArcticDEM terrain data DEM(s) were created from DigitalGlobe, Inc., imagery and
  funded under National Science Foundation awards 1043681, 1559691, and 1542736;
* Australia terrain data © Commonwealth of Australia (Geoscience Australia) 2017;
* Austria terrain data © offene Daten Österreichs – Digitales Geländemodell (DGM)
  Österreich;
* Canada terrain data contains information licensed under the Open Government
  Licence – Canada;
* Europe terrain data produced using Copernicus data and information funded by the
  European Union - EU-DEM layers;
* Global ETOPO1 terrain data U.S. National Oceanic and Atmospheric Administration
* Mexico terrain data source: INEGI, Continental relief, 2016;
* New Zealand terrain data Copyright 2011 Crown copyright (c) Land Information New
  Zealand and the New Zealand Government (All rights reserved);
* Norway terrain data © Kartverket;
* United Kingdom terrain data © Environment Agency copyright and/or database right
  2015. All rights reserved;
* United States 3DEP (formerly NED) and global GMTED2010 and SRTM terrain data
  courtesy of the U.S. Geological Survey.
```

## 本项目的修改

- 按经纬度裁切瓦片并拼接
- 双线性重采样到 512 × 512
- 归一化为 uint16，gzip 压缩后以 base64 内嵌
- 按高程/坡度/朝向生成岩石、雪、冰川颜色；垂直夸张、雪线、光照、等高线为视觉处理
- 未修改原始 DEM 数值以外的地形含义

## 代码

- three.js r160，MIT License，https://threejs.org
- esbuild 0.28（仅构建时使用），MIT License，https://esbuild.github.io

本项目其余代码为页面自身实现。