# Layers and RAT metadata

In CRAN or offline builds, network-dependent chunks are not evaluated.

This example uses BlueTopo tiles covering New York Harbor. The workflow demonstrates tile discovery, checksum-verified asset retrieval, and file-backed raster access with `terra`. It opens elevation, uncertainty, and contributor layers, then reads Raster Attribute Table (RAT) sidecars for contributor metadata. Elevation is shown with hillshade and contours; uncertainty and contributor IDs are plotted as their own source layers.

The contributor band contains IDs, not continuous values. Contributor IDs must not be averaged. RAT sidecars carry contributor metadata, and `bluertopo` preserves original RAT files.

## Example area

## All layers

    all_layers <- bluertopo(
      real_aoi,
      layers = "all",
      coverage = "fill",
      details = TRUE,
      progress = FALSE,
      quiet = TRUE
    )

## RAT sidecar manifest

## Contributor lookup

## Elevation

## Uncertainty

## Contributor IDs

Contributor values are identifiers that point into RAT metadata. They are not continuous terrain values.