Struct SrtmServiceBuilder 

pub struct SrtmServiceBuilder { /* private fields */ }

Builder for creating SrtmService with custom configuration.

Example

use htg::SrtmServiceBuilder;

let service = SrtmServiceBuilder::new("/data/srtm")
    .cache_size(100)
    .build();

With Auto-Download (requires download feature)

use htg::{SrtmServiceBuilder, download::DownloadConfig};

let service = SrtmServiceBuilder::new("/data/srtm")
    .cache_size(100)
    .auto_download(DownloadConfig::with_url_template(
        "https://example.com/srtm/{filename}.hgt.gz", // compression auto-detected
    ))
    .build()?;

Implementations

impl SrtmServiceBuilder

pub fn new<P: AsRef<Path>>(data_dir: P) -> Self

Create a new builder with the specified data directory.

pub fn from_env() -> Result<Self>

Create a builder configured from environment variables.

Environment Variables

Variable	Description	Default
HTG_DATA_DIR	Directory containing .hgt files	Required
HTG_CACHE_SIZE	Maximum tiles in cache	100
HTG_DOWNLOAD_SOURCE	Named source: “ardupilot”*	None
HTG_DOWNLOAD_URL	URL template for custom downloads*	None
HTG_DOWNLOAD_GZIP	Whether URL serves gzip files*	false

*Only used when download feature is enabled.

Named Sources

• ardupilot or ardupilot-srtm1 - ArduPilot SRTM1 (30m resolution, ~25MB/tile)
• ardupilot-srtm3 - ArduPilot SRTM3 (90m resolution, ~2.8MB/tile)

URL Template Placeholders

• {filename} - Full filename (e.g., “N35E138”)
• {lat_prefix} - N or S
• {lat} - Latitude digits (e.g., “35”)
• {lon_prefix} - E or W
• {lon} - Longitude digits (e.g., “138”)
• {continent} - Continent subdirectory (e.g., “Eurasia”, “North_America”)

Example

# Using ArduPilot source (recommended)
export HTG_DATA_DIR=/data/srtm
export HTG_DOWNLOAD_SOURCE=ardupilot

# Or using custom URL template
export HTG_DATA_DIR=/data/srtm
export HTG_CACHE_SIZE=50
export HTG_DOWNLOAD_URL="https://example.com/srtm/{filename}.hgt.gz"

use htg::SrtmServiceBuilder;

let service = SrtmServiceBuilder::from_env()?.build()?;

Errors

Returns an error if HTG_DATA_DIR is not set.

pub fn data_dir<P: AsRef<Path>>(self, path: P) -> Self

Set the data directory.

Overrides the directory set in the constructor or from environment.

pub fn cache_size(self, size: u64) -> Self

Set the maximum number of tiles to keep in cache.

Default is 100 tiles.

pub fn build(self) -> SrtmService

Build the SrtmService.