Retrieving and Sharing Data

ESRI uses metadata from map services to provide information about the data.

share your data

package your map

import map package 📦

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File and data formats 📁

• Shapefiles: Use for simple projects or when compatibility with other GIS software is required.
• Personal Geodatabases: Use for small to medium projects, especially when integration with Microsoft Access is needed.
• File Geodatabases: Use for large datasets, complex projects, and modern workflows due to their superior performance and flexibility.

Feature	Shapefile	Personal Geodatabase	File Geodatabase
File Format	Multiple files (e.g., .SHP, .DBF, .PRJ, etc.)	Single file (.MDB)	Folder containing multiple files (managed by ArcGIS)
Storage Technology	Old database technology	Based on Microsoft Access (old storage technology)	Modern storage technology
Data Types Supported	Vector only (points, lines, polygons)	Vector, raster, tables, and Esri-specific data types	Vector, raster, tables, and Esri-specific data types
Number of Feature Classes	Single feature class per shapefile	Multiple feature classes	Multiple feature classes
File Size Limit	2GB per component file	2GB for the entire database	Virtually unlimited (limited by disk space)
Field Name Limit	13 characters	64 characters	64 characters
Compression	No compression	Greater compression than shapefiles	Highest compression among the three
Performance	Slower for large datasets	Faster than shapefiles	Fastest for large datasets
Compatibility	Widely supported across GIS software	Compatible with Microsoft Access	Requires ArcGIS or compatible software
Ease of Sharing	Requires zipping multiple files	Single file, easy to share	Requires zipping the folder
Use Case	Simple projects, widely supported format	Small to medium projects, integration with Microsoft Access	Large datasets, complex projects, modern workflows
Metadata Support	Limited	Better than shapefiles	Best metadata support
Raster Data Support	Not supported	Supported	Supported
Editing and Querying	Limited	Advanced (via Microsoft Access)	Advanced (via ArcGIS)

joins and relates

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https://www.coursera.org/learn/gis/lecture/u0Axq/joins-and-relates

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Key Points:

1. Joins and Relates in GIS:

   • Joins: Combine tables by adding columns from one table to another based on a common ID column.
   • Relates: Establish a connection between two tables to pass selections or summarize information without physically merging the tables.

2. Tables and Data Sources:

   • Tables can be attribute tables associated with feature classes, independent tables (e.g., CSV files), or tables within a file geodatabase.
   • Joins and relates are used to connect different data sources for analysis or symbology in GIS.

3. Common ID Column:

   • Both joins and relies on a common ID column to link tables.
   • The ID column names do not need to be identical but must contain matching values.

4. One-to-Many Relationships:

   • Relates are particularly useful for one-to-many relationships, where one record in a table corresponds to multiple records in another table (e.g., one zone with multiple observations).

5. Practical Applications:

   • Joins: Useful for adding additional attributes to a feature class (e.g., adding drainage area data to rivers).
   • Relates: Useful for summarizing or analyzing related data (e.g., linking watersheds to species observations).

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Steps for Joins and Relates in ArcGIS Pro:

Joins:

1. Identify Common ID:
   • Ensure both tables have a common ID column with matching values.
2. Add Join:
   • Right-click the target layer (e.g., rivers) > Joins and Relates > Add Join.
   • Select the input table (e.g., cumulative area table) and the common ID column.
3. Validate Join:
   • Use the validate tool to check for one-to-one or one-to-many matches.
4. Review Results:
   • Open the attribute table to verify the joined columns.
   • Use Select by Attributes to check for unmatched records.

Relates:

1. Identify Common ID:
   • Identify the common ID column between the two tables (e.g., HUC 12 and Zone ID).
2. Add Relate:
   • Right-click the target layer (e.g., subwatersheds) > Joins and Relates > Add Relate.
   • Set the input and output fields, and define the relationship (e.g., one-to-many).
3. Use Relate:
   • Select features in the primary table (e.g., subwatersheds).
   • Use the Related Data option to view corresponding records in the related table (e.g., species observations).

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Exercises:

1. Join Exercise:

   • Load a feature class (e.g., rivers) and a CSV file with additional attributes (e.g., drainage area).
   • Perform a join to add the drainage area data to the rivers attribute table.
   • Validate the join and check for unmatched records.

2. Relate Exercise:

   • Load a feature class (e.g., watersheds) and a table with observations (e.g., species data).
   • Establish a relate between the watersheds and observations using a common ID.
   • Select watersheds and use the relate to view corresponding observations.

3. Data Analysis:

   • Use joined data to create symbology (e.g., color-code rivers by drainage area).
   • Use relates to summarize observations within selected watersheds.

4. Error Checking:

   • Practice identifying and resolving issues with joins and relates (e.g., mismatched IDs, null values).

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Summary:

• Joins physically combine tables by adding columns.
• Relates create a dynamic connection between tables for analysis.
• Both rely on a common ID column and are essential for managing and analyzing spatial and tabular data in GIS.