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2. Map Layers

Goal: Confidently add, reorder, group, and tune layers in the Contents pane.

What is a layer?

A layer is a reference to data plus its display settings. The layer in your map is not the file itself — it points to a source on disk or in a database. You can have many layers pointing to the same source with different styling.

Adding data

Method Use case
Map → Add Data Browse and add one or more
Drag from Catalog Pane Fastest
Map → Add Data → XY Point Data CSV with lat/long
Map → Basemap Add a base layer
Map → Add Data → Data From Path Paste a full path (UNC, AGOL URL)

Drawing order

Layers in the Contents pane draw top-down:

  • The top layer in Contents is the top layer on the map.
  • Drag layers up and down to reorder.
  • Polygons usually go bottom, lines middle, points top.
  • The basemap stays at the bottom.

Layer groups

Right-click in Contents → New Group Layer. Drag layers into the group. Use this to:

  • Bundle related layers (e.g., all transportation)
  • Toggle whole sets on/off at once
  • Apply the same scale-range to several layers

Layer properties

Right-click a layer → Properties. Tabs you'll use:

Tab What
General Name, description, scale visibility, snap-to-feature
Source File path, CRS, total feature count
Time Time-aware settings (animations)
Display Transparency, ordering, popups, labels-from-features
Symbology Open the symbology pane (covered next)
Definition Query SQL filter (covered in Select by Attributes)

Visibility scale ranges

Set min/max scale to only show a layer when zoomed to a useful range:

  • Min scale: zoom out limit (large number, e.g., 1:500,000)
  • Max scale: zoom in limit (small number, e.g., 1:5,000)

Useful for keeping detailed layers from cluttering small-scale views.

Quick layer styling

Single-symbol changes are quickest from the Contents pane:

  1. Click the colored symbol below the layer name.
  2. Pick a color, line width, or marker style.
  3. Done.

For more control, open Symbology (next lesson).

Special layer types

Type Notes
Feature layer Vector — points/lines/polygons
Raster layer A single raster file
Mosaic dataset Many rasters managed as one
Service layer Hosted on AGOL or ArcGIS Server
Group layer Container only
Annotation layer Stored, geometric labels

Layer files (.lyrx)

You can save a layer's style to a .lyrx file (right-click → Sharing → Save As Layer File). Apply it later or share with teammates so the styling matches across projects.

Practice

Try this

  1. Create a new map.
  2. Add a basemap (Topographic).
  3. Add three layers: counties (polygon), interstates (line), airports (point).
  4. Reorder them so all three draw correctly.
  5. Group them under a new Group Layer called "Reference data".
  6. Set min scale on counties to 1:5,000,000 (so the layer disappears when zoomed way out).

→ Next: Symbology.