GIS Analysis Functions: Fundamentals

GIS analysis functions are essential tools for extracting meaningful information from geographic data

They enable users to manipulate, transform, and combine data layers to answer specific questions and make informed decisions.

Here are some fundamental analysis functions:


Retrieval

  • Querying: Extracting specific features or attributes based on predefined criteria:
    • Example: Selecting all restaurants with a rating of 4 stars or higher from a database of restaurants.
  • Spatial selection: Identifying features that intersect, overlap, or are contained within a specific area:
    • Example: Finding parcels that fall within a flood zone by overlaying a flood hazard map with a parcel map.

Reclassification

Buffering and Neighborhood

  • Buffering: Creating zones of a specified distance around features:
    • Example: Generating buffers around schools to identify potential noise pollution areas.
  • Neighborhood analysis: Examining the characteristics of features within a specified proximity:

Overlaying

  • Union: Combining multiple layers to create a new layer containing all features from the input layers:
    • Example: Merging land use and soil type maps to identify areas suitable for agriculture.
  • Intersection: Identifying features that overlap between two or more layers:
  • Difference: Identifying features that are unique to one layer:
    • Example: Finding areas that are zoned for commercial use but are not currently developed.















By effectively using these analysis functions, GIS users can gain valuable insights into spatial relationships, patterns, and trends, supporting decision-making in various fields such as urban planning, environmental management, and resource allocation.

Retrieval Function
Civil Engineering DomainExample of GIS Retrieval FunctionCriteria Used
Structural EngineeringIdentify all buildings within a 500-meter radius of a proposed bridge abutment that were built before 1980 and have four or more stories to prioritize for seismic retrofitting assessment.Spatial Query (within 500m of a feature) AND Attribute Query (Construction Year < 1980 AND Height ≥ 4 stories).
Transportation EngineeringSelect all road segments classified as "arterial" where the Pavement Condition Index (PCI) is less than 50 to target them for immediate maintenance and resurfacing projects.Attribute Query (Road Class = 'Arterial' AND PCI < 50).
Water Resources EngineeringExtract all drainage culverts that have a diameter less than 0.75 meters and are located within a designated 100-year floodplain to assess flood vulnerability and capacity for upgrade.Attribute Query (Diameter < 0.75m) AND Spatial Query (Intersecting the 100-year Floodplain boundary).
Environmental EngineeringRetrieve all industrial sites that have been issued an air emissions permit and are located upwind of a residential zone to monitor air quality compliance.Attribute Query (Permit Type = 'Air Emissions') AND Spatial Query (Upwind/Directional relationship to 'Residential Zone' polygons).
Geotechnical EngineeringFind all boreholes or soil samples within a proposed construction site where the Standard Penetration Test (SPT) N-value is less than 10 (indicating very loose soil) to guide deep foundation design.Spatial Query (within Site Boundary) AND Attribute Query (SPT N-value < 10).
Construction Engineering & ManagementIdentify all utility lines (electric, gas, water) that cross the path of a trench scheduled for excavation next week, allowing the manager to arrange for utility locating and shut-off procedures.Spatial Query (Intersecting the 'Trench Path' line feature) AND Attribute Query (Utility Type = ANY).
Materials Science & EngineeringSelect all concrete bridge decks that were built using a specific low-quality aggregate supplier (Supplier ID 'X') and have exhibited a cracking index greater than 0.5 to determine the performance failure correlation.Attribute Query (Aggregate Supplier = 'X' AND Cracking Index > 0.5).
Coastal EngineeringRetrieve all structures built closer than 100 meters to the current shoreline that have a recorded elevation below 3 meters Mean Sea Level (MSL) to assess immediate risk from sea-level rise and storm surge.Spatial Query (within 100m of 'Shoreline') AND Attribute Query (Elevation < 3m MSL).
Urban (Municipal) EngineeringIdentify all maintenance work orders issued in the last quarter for water main breaks on pipes with a material type of 'Cast Iron' within the central business district.Attribute Query (Maintenance Date ≥ Q4 Start AND Pipe Material = 'Cast Iron' AND Work Type = 'Break').
Surveying & Geomatics EngineeringSelect all GPS control points that have an recorded vertical accuracy less than ± 5mm within the project area for use as high-precision benchmarks.Spatial Query (within Project Area) AND Attribute Query (Vertical Accuracy < 5mm).
Earthquake EngineeringRetrieve all schools and hospitals located within 10 km of a known active fault line to prioritize for immediate seismic hazard assessment.Spatial Query (within 10 km of 'Active Fault' line features).
Infrastructure EngineeringFind all fiber optic cable segments that have been in service for over 15 years and pass underneath a railroad track for preventative replacement planning.Attribute Query (Service Life ≥ 15 years) AND Spatial Query (Intersecting 'Railroad Track' line features).
Buffering Function
Civil Engineering DomainExample of GIS Buffering FunctionFeature Buffered & Buffer Width
Structural EngineeringEstablishing a construction Setback Zone around the perimeter of a wetland or property boundary where temporary construction activities (e.g., equipment staging) are prohibited.Feature: Wetland Polygon. Width: 30-meter setback (inward buffer).
Transportation EngineeringCreating a Noise Contamination Zone around a proposed new highway alignment to identify all residential properties that will be impacted by excessive traffic noise.Feature: Proposed Highway Line. Width: 200-meter buffer (outward).
Water Resources EngineeringCreating a Riparian Buffer or Environmental Protection Area along a river or stream where development is restricted to protect water quality and aquatic habitats.Feature: River/Stream Line. Width: 50-meter buffer (outward) on both sides.
Environmental EngineeringDefining a Hazardous Plume Impact Zone around a known contaminated groundwater source to restrict well drilling and assess the area for remediation.Feature: Contaminant Source Point. Width: Variable buffer distance based on plume modeling extent.
Geotechnical EngineeringEstablishing a Slope Stability Buffer around the crest of a large, unstable excavated slope where no heavy machinery or dynamic loading is permitted.Feature: Crest of Slope Line. Width: 15-meter buffer (outward/down-slope).
Construction Engineering & ManagementCreating a Right-of-Way (ROW) Acquisition Buffer around a planned pipeline or utility path to calculate the exact land area that needs to be purchased or leased.Feature: Pipeline Centerline. Width: 10-meter fixed buffer (outward) on both sides.
Materials Science & EngineeringIdentifying all asphalt pavement sections that fall within a close proximity of a salt storage facility to analyze premature pavement wear caused by salt spray/runoff.Feature: Salt Storage Facility Point/Polygon. Width: 150-meter buffer (outward).
Coastal EngineeringDefining a No-Build Zone landward of the current Mean High Water (MHW) line to account for expected 50-year sea-level rise and coastal erosion.Feature: Mean High Water (MHW) Line. Width: Variable buffer distance based on erosion model (outward/landward).
Urban (Municipal) EngineeringDetermining the Service Area for a newly proposed fire station to ensure it meets the city's requirement of providing service within a 5-minute drive time.Feature: Proposed Fire Station Point. Width: Travel time buffer (e.g., 5-minute street network distance).
Surveying & Geomatics EngineeringGenerating a Visual Obstruction Zone buffer around a communication tower to comply with FAA regulations limiting the height of surrounding structures.Feature: Communication Tower Point. Width: Buffer distance corresponding to a required sight line angle.
Earthquake EngineeringCreating a Fault Rupture Hazard Zone buffer along mapped active fault lines where building construction is subject to stringent regulations or prohibitions.Feature: Active Fault Line. Width: 50-meter buffer (outward) on both sides based on regulatory standards.
Infrastructure EngineeringEstablishing an Exclusion Zone around a critical power substation to prevent high-impact land uses and protect the facility's security and maintenance access.Feature: Substation Polygon. Width: 100-meter buffer (outward/perimeter).
Overlay Function
Civil Engineering DomainExample of GIS Overlay FunctionInput Layers & Output
Structural EngineeringZonal Mapping for Foundation Design: Combining a map of Subsurface Soil Types with a map of Seismic Hazard Zones to determine the required foundation type (e.g., deep piles vs. shallow footings) for every area on a new project site.Input 1: Soil Type Polygons. Input 2: Seismic Zone Polygons. Output: Foundation Design Zone Map.
Transportation EngineeringIntersection Accident Analysis: Overlaying a layer of Traffic Accident Points (with attributes like injury severity) onto a layer of Road Geometry Segments (with attributes like curve radius) to identify high-risk intersections and correlation between design flaws and crash frequency.Input 1: Accident Points. Input 2: Road Network Lines. Output: Road Segments with aggregated accident statistics.
Water Resources EngineeringWetlands Impact Assessment: Intersecting a Proposed Development Footprint (polygon) with a Regulated Wetlands Inventory (polygon) to calculate the precise area of wetland that will be directly disturbed by construction.Input 1: Development Polygon. Input 2: Wetlands Polygon. Output: Polygon showing the overlap area and its size.
Environmental EngineeringGroundwater Contamination Risk: Combining a map of Porous Aquifer Zones (high vulnerability) with a map of Underground Storage Tank (UST) Locations to create a prioritized list of areas for monitoring.Input 1: Aquifer Vulnerability Polygons. Input 2: UST Location Points. Output: UST points flagged with the underlying vulnerability level.
Geotechnical EngineeringTrenching Difficulty Mapping: Overlaying a layer of Bedrock Depth Contours with a layer of Groundwater Table Elevation to determine where trench excavation will likely encounter both rock and saturated soil, indicating high cost/difficulty.Input 1: Bedrock Depth Raster. Input 2: Water Table Raster. Output: Raster representing excavation difficulty (Arithmetic/Logical Overlay).
Construction Engineering & ManagementConflicting Utilities and Excavation: Overlaying the Planned Excavation Trench Lines onto a comprehensive map of Existing Utility Lines (gas, electric, fiber) to identify all exact points of conflict requiring expensive cross-bracing or line relocation.Input 1: Trench Line. Input 2: All Utility Lines. Output: Intersection points with combined attributes (Utility ID and Trench ID).
Materials Science & EngineeringCorrosion Risk Mapping: Combining a map of High-Salinity Soil Zones with a map of Buried Steel Pipeline Segments to identify areas where specialized corrosion-resistant pipe coatings are mandatory.Input 1: Salinity Zone Polygons. Input 2: Pipeline Line Segments. Output: Pipeline segments categorized by corrosion risk level.
Coastal EngineeringTsunami Vulnerability Assessment: Combining a layer showing the Tsunami Inundation Extent (maximum expected flood zone) with a layer of Critical Lifeline Infrastructure (hospitals, shelters) to determine which facilities will be rendered inoperable.Input 1: Inundation Polygon. Input 2: Critical Infrastructure Points. Output: List of points falling inside the inundation zone.
Urban (Municipal) EngineeringZoning Compliance Check: Intersecting a proposed Building Footprint with the Official Zoning Map to automatically merge the building's attributes (e.g., height, use) with the local regulatory requirements for that specific zone.Input 1: Building Polygon. Input 2: Zoning Polygon. Output: Merged polygon containing both feature and zoning code attributes.
Surveying & Geomatics EngineeringProperty Value Appraisal: Overlaying a Parcel Boundary Map with a Floodplain Map to attach the regulatory risk attribute ("In Floodplain" or "Not In Floodplain") directly to each property record for appraisal purposes.Input 1: Parcel Polygons. Input 2: Floodplain Polygon. Output: Parcel attributes updated with Floodplain status.
Earthquake EngineeringTotal Seismic Risk Score: Using a weighted overlay (often raster-based) to combine layers representing Liquefaction Potential, Ground Shaking Intensity, and Proximity to Fault to create a single composite map of total seismic hazard.Input 1-3: Weighted Hazard Raters. Output: Final Total Seismic Hazard Raster.
Infrastructure EngineeringMaintenance Responsibility: Combining layers of Utility Ownership Boundaries (e.g., City, State, Private) with a map of Storm Sewer Manholes to instantly determine the entity responsible for maintenance and inspection of each asset.Input 1: Ownership Boundary Polygons. Input 2: Manhole Points. Output: Manhole points with the responsible entity's name as an attribute.
Reclassification Function
Civil Engineering DomainExample of GIS Reclassification FunctionOriginal Values → Reclassified Values
Structural EngineeringReclassifying building material codes to simplify structural vulnerability assessment categories for city planning.Concrete, Steel, Timber → High Stiffness, Medium Stiffness, Low Stiffness
Transportation EngineeringReclassifying traffic volume data into service level ratings to prioritize road capacity upgrades.Annual Average Daily Traffic (AADT) in numbers → Level A (Free Flow), Level B (Stable Flow), Level C (Near Capacity), Level D (Congested)
Water Resources EngineeringReclassifying soil permeability rates to assess infiltration and runoff potential for stormwater modeling.Hydraulic Conductivity (mm/hr) in 0.1 increments → Low, Medium, High Infiltration Potential
Environmental EngineeringReclassifying land cover types into a Runoff Coefficient value for hydrological modeling of urban areas.Asphalt, Forest, Grass → 0.90, 0.15, 0.25 (Runoff Coefficient value)
Geotechnical EngineeringReclassifying slope angle data (derived from a Digital Elevation Model) to create a suitability map for deep excavation.Slope Angle in degrees (0∘−5∘, 5∘−15∘, >15∘) → Suitable, Conditional, Unsuitable
Construction Engineering & ManagementReclassifying contractor past performance scores into risk categories for bidding evaluation.Performance Score (90−100, 70−89, <70) → Low Risk, Moderate Risk, High Risk
Materials Science & EngineeringReclassifying concrete strength test results based on minimum design criteria.Compressive Strength (e.g., 30 MPa, 35 MPa, 40 MPa) → Pass, Pass, Pass (or Fail if below minimum)
Coastal EngineeringReclassifying bathymetry (water depth) data to identify areas suitable for beach nourishment or structure placement.Depth in meters (e.g., 0−5 m, 5−10 m, >10 m) → Shallow Zone, Nearshore Zone, Deep Zone
Urban (Municipal) EngineeringReclassifying water pipe age into priority groups for infrastructure replacement programs.Age in years (0−25, 26−50, >50) → Low Priority, Medium Priority, High Priority
Surveying & Geomatics EngineeringReclassifying elevation data into elevation zones for visualization on a topographic map.Elevation in meters → Zone 1 (e.g., 0−100 m), Zone 2 (101−200 m), etc.
Earthquake EngineeringReclassifying proximity to an active fault based on regulatory setback requirements.Distance to Fault (e.g., 0−50 m, 50−100 m, >100 m) → Exclusion Zone, Restricted Zone, General Zone
Infrastructure EngineeringReclassifying various land use types into generalized categories for regional planning models.Single-Family Residential, Multi-Family Residential, Mixed-Use Commercial → Residential, Residential, Commercial
Neighbourhood Function
Civil Engineering DomainExample of GIS Neighborhood FunctionFunction & Neighborhood Definition
Structural EngineeringSlope and Aspect Calculation: Analyzing a Digital Elevation Model (DEM) to determine the steepest slope (Max) and direction (Aspect) for every point within a proposed foundation site.Function: Focal Max/Slope/Aspect. Neighborhood: 3×3 or 5×5 cell window.
Transportation EngineeringVehicle Crash Density: Calculating the Count (Density) of all traffic accidents within a 200-meter radius of every road segment to identify high-hazard corridors, regardless of the segment's classification.Function: Point Density (Count). Neighborhood: 200-meter circular area.
Water Resources EngineeringFlow Accumulation (Watershed Modeling): Calculating the total number of upstream cells that drain into each cell of a raster (representing the cumulative water volume).Function: Flow Accumulation. Neighborhood: Defined by the direction of flow from adjacent cells.
Environmental EngineeringAir Pollution Interpolation: Using ambient air quality measurements from point stations to calculate the Average (Interpolation) pollution level across an entire urban area, effectively smoothing localized readings.Function: Interpolation (e.g., Inverse Distance Weighting). Neighborhood: Defined by distance and number of surrounding measurement points.
Geotechnical EngineeringSoil Quality Smoothing: Applying a Focal Mean (Average) filter to a raster of soil shear strength values to smooth out localized sampling errors and better represent the general shear strength across a large area.Function: Focal Mean. Neighborhood: 3×3 or 5×5 cell window.
Construction Engineering & ManagementOptimal Crane Placement: Determining the Closest (Nearest Neighbor) distance from every point on the job site to the nearest accessible street or staging area to plan logistics routes for large deliveries.Function: Nearest Neighbor/Cost Distance. Neighborhood: Defined by proximity to access points.
Materials Science & EngineeringTemperature Influence on Pavement: Calculating the Maximum recorded pavement surface temperature within a defined weather reporting zone over a summer to assess the stress on asphalt materials.Function: Zonal Max (Statistic on surrounding area). Neighborhood: Defined by a weather zone boundary polygon.
Coastal EngineeringWave Energy Exposure: Calculating the Average (Focal Mean) wave height or energy over a 100-meter stretch of coastline to define consistent levels of stress on coastal defenses like breakwaters.Function: Focal Average. Neighborhood: 100-meter linear segment or circular radius.
Urban (Municipal) EngineeringService Accessibility: Creating Thiessen Polygons (Proximal Allocation) around existing schools or parks to define the area closest to each facility, demonstrating neighborhood service coverage.Function: Thiessen Polygons. Neighborhood: Defined by the nearest point feature.
Surveying & Geomatics EngineeringElevation Error Analysis: Calculating the Standard Deviation (Focal Statistical) of elevation values within a small window of a LiDAR-derived DEM to identify areas of excessive noise or potential error spikes.Function: Focal Standard Deviation. Neighborhood: 3×3 cell window.
Earthquake EngineeringLocalized Building Age Assessment: For a specific building, finding the Average (Zonal Mean) construction age of all buildings within a 150-meter radius to estimate the general vulnerability of the immediate neighborhood.Function: Zonal Statistics (Average). Neighborhood: 150-meter circular buffer around the target building.
Infrastructure EngineeringProximity to Critical Facilities: For every segment of a proposed new utility corridor, calculating the Minimum (Nearest Neighbor) distance to the closest hospital or school to ensure security and minimize disruption risk.Function: Near/Distance Calculation. Neighborhood: Defined by proximity to critical point features.

A Deeper Dive into GIS Overlay Analysis for the Tapti River Questions

Some more functions.



When to Use GIS Analysis Functions

  • Understanding spatial relationships: To identify patterns, trends, and correlations between geographic features (e.g., analyzing the relationship between crime rates and socioeconomic factors).
  • Evaluating spatial distribution: To assess the distribution of resources or phenomena across a geographic area (e.g., examining the distribution of healthcare facilities in a region).
  • Assessing impact: To evaluate the potential impacts of proposed projects or policies (e.g., assessing the environmental impact of a new development).
  • Optimizing resource allocation: To allocate resources efficiently based on spatial factors (e.g., identifying the optimal location for a new school or fire station).
  • Supporting decision-making: To provide data-driven insights for informed decision-making (e.g., selecting the best route for a new road or identifying areas at risk of flooding).

Why Use GIS Analysis Functions

  • Efficiency: GIS analysis functions automate tasks, saving time and effort.
  • Accuracy: GIS provides precise spatial data, ensuring accurate analysis results.
  • Integration: GIS can integrate data from various sources, allowing for comprehensive analysis.
  • Visualization: GIS tools enable the creation of informative maps and visualizations, facilitating understanding.
  • Decision support: GIS analysis provides valuable insights for informed decision-making.

How to Use GIS Analysis Functions

  1. Identify the research question or problem: Clearly define what you want to investigate.
  2. Gather relevant data: Collect necessary geographic data layers (e.g., maps, satellite imagery, census data).
  3. Choose appropriate analysis functions: Select the GIS functions that align with your research question (e.g., overlaying, buffering, spatial join).
  4. Execute the analysis: Apply the chosen functions to your data using GIS software.
  5. Interpret the results: Analyze the output and draw conclusions based on the findings.
  6. Visualize the results: Create maps or charts to communicate your findings effectively.



References.


https://maps.unomaha.community/Peterson/gis/notes/GISAnal1.html

https://maps.unomaha.community/Peterson/gis/notes/GISAnal1_2.html

http://www.gitta.info/AnalyConcept/en/html/Overview_learningObject3.html



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