In the competitive geospatial world, having a solid foundation in basic GIS knowledge and being well-prepared with commonly asked GIS interview questions can make all the difference. Understanding the fundamentals of GIS concepts, tools, and applications is essential to showcase your expertise and demonstrate your problem-solving skills. By familiarizing yourself with a range of GIS interview questions, you can gain confidence and effectively articulate your abilities during the interview. So, equip yourself with the knowledge and practice you need to excel in your next GIS interview. Explore a comprehensive collection of GIS interview questions to enhance your preparation and boost your chances of success

What is GIS?

GIS, which stands for Geographic Information System, is a technology that integrates location-based data to create intelligent maps and models. It helps analyze, interpret, and visualize geospatial information, enabling informed decision-making in various industries. It helps us answer questions like “Where?” and “What’s there?” by combining different types of information, such as maps, satellite images, and numbers. 

With GIS, we can see patterns, find the best routes, plan cities, and make important decisions. It’s like a digital map toolbox that helps us explore and understand our world better.

What can GIS do?

GIS works with different applications: land use planning, environmental management, sociological analysis, business marketing, weather prediction, city planning, waste-water planning, urban planning, navigation tools, and many more.

What are Map data types?

This is a little bit tricky because most people confuse themselves with map data types and data formats. There are two types of map data: Discrete and Continuous.

Discrete: objects in the real world with specific locations or boundaries, such as cities, roads, or soil units

Continuous: the quantity that is measured and recorded everywhere over a surface, such as a temp or elevation

What are Data formats?

There are two data formats that GIS is handy with Vector and Raster data formats. Both data systems store spatial and attribute data but in different ways. Both are geo-referenced, meaning that the information is tied to a specific location on the earth’s surface using x-y coordinates defined in a standard way: a coordinate system.

Vector model:

stores discrete data—eg, points (no dimension), lines (1D), and polygons (2D).

Benefits of vector models:

• Precise representation of geographic features
• Ability to store attribute information along with geometric data
• Preservation of topological relationships between features
• Efficient storage and data handling
• Versatility in representing different types of geographic phenomena

Drawbacks:

• Poorly adapted to storing continuous surfaces, such as elevation or precipitation.
• Spatial analysis operations on vector data can be computationally intensive.
• Loss of information or simplification may occur when converting continuous data to vector format.
• Large vector datasets with numerous features can require significant storage space.

Raster Model:

stores continuous data—a set of spatial data represented as a series of small squares called cells or pixels. Each pixel contains a numeric code indicating a single attribute, and the raster is stored as an array of numbers. Eg, DEM.

Benefits of Raster models:

• Efficiently represent continuous and spatially distributed phenomena, such as elevation, temperature, and satellite imagery.
• Easy storage and compression of large datasets.
• Support for cell-based calculations and analysis operations.
• Ability to define and analyze multiple attributes associated with each cell.
• Seamless integration of remotely sensed data.
• Effective data visualization through color ramps and shading.
• Suitable for modeling and simulation of continuous processes, such as hydrological modeling or climate simulations.

Drawbacks:

• Suffer from trade-offs between precision and storage space to a greater extent than vectors do.
• Can store only one numeric attribute per raster, whereas vectors can store hundreds of attribute values for each spatial feature and can handle text data more efficiently.
• Limited representation of complex or irregular features.
• Reduced precision for fine-scale spatial details.
• Limited handling of varying resolutions or projections.
• Data distortion when resampling or reprojecting.

What are feature classes?

Feature classes in GIS are data structures that organize and store similar types of geographic features, such as points, lines, or polygons. They provide a consistent format for representing spatial information and associated attributes. 

Think of feature classes as categorized containers that hold specific types of geographic elements, making it easier to manage, analyze, and visualize different types of features within a GIS environment.

What are attributes?

GIS attributes are additional details about geographic features. They include names, labels, or values that describe specific characteristics. Attributes help categorize and analyze features, enhancing data understanding and visualization in GIS.

What is map scale?

Map scale refers to the relationship between the distance on a map and the corresponding distance on the ground in the real world. Map scale is like a magnifying glass for a map. It tells you how much the map has been shrunk or zoomed in compared to the actual terrain. For example, a scale of 1:10,000 means that one unit on the map represents 10,000 units in the real world. This could be inches, centimeters, or any other unit of measurement.

Large-scale maps (with smaller denominators) show a relatively small area, such as a quadrangle, whereas small-scale maps (with large denominators) show relatively larger areas, such as states or countries.

What is Resolution?

Resolution in GIS refers to the level of detail captured or displayed in a spatial dataset. It determines the clarity and accuracy of the data.

• Spatial Resolution: Refers to the level of detail in a spatial dataset. For example, a satellite image with a spatial resolution of 1 meter means that each pixel in the image represents an area of 1 square meter on the ground.
• Temporal Resolution: Indicates the frequency of data collection or updates over time. For instance, weather data collected every hour has a higher temporal resolution compared to data collected once a day.
• Spectral Resolution: Describes the range and granularity of wavelengths captured by remote sensing instruments. Hyperspectral imagery, with hundreds of narrow spectral bands, offers high spectral resolution for detailed analysis of specific features or materials.
• Radiometric Resolution: Refers to the sensitivity of the sensor in detecting and representing variations in radiation. A digital elevation model (DEM) with a higher radiometric resolution, such as 16 bits, can represent elevation values more accurately than a DEM with a lower resolution, like 8 bits.

What is precision?

Precision in GIS refers to the level of consistency and exactness in measurements or data representations. It indicates how closely values match within a dataset or repeated measurements.

For example, if you measure the length of a pencil multiple times and consistently get results between 14.8 and 15.2 centimeters, it demonstrates a high level of precision. On the other hand, if your measurements vary widely, such as ranging from 13 to 16 centimeters, it indicates a lower level of precision with more variability in the data.

What is metadata?

Metadata is a data of the data which stores information about the dataset, such as where it came from, how it was developed, who assembled it, how precise it is, and whether it can be given to another person It provides details about the data’s source, quality, content, and structure. Think of metadata as the “data about the data.” It helps users understand and effectively use the dataset by providing essential information for data discovery, evaluation, and interpretation.

Also, explore GIS opportunities in Government Departments: Government GIS Jobs

What are shapefiles?

Shapefiles are a widely used geospatial data format in GIS. They store both the geometry and attribute information of geographic features in a set of files. With their versatility and compatibility, shapefiles are popular for sharing and analyzing spatial data across different GIS platforms.

Shapefiles consist of the following parts:

• Geometric Data (.shp): Stores the spatial representation of features like points, lines, or polygons.
• Attribute Data (.dbf): Contains attribute information associated with each feature, such as names, IDs, or other descriptive data.
• Index Files (.shx): Optional files that provide indexing for faster access to the geometric data.
• Projection File (.prj): Optional file that defines the coordinate system and projection used for spatial reference.
• Metadata File (.xml): Optional file that contains descriptive information about the shapefile, aiding in understanding its content and context.

What are geodatabases?

Geodatabases are specialized databases for storing and managing geospatial data in GIS. There are 3 types of geodatabases:

1. Personal geodatabases: designed by use by individuals or small workgroups and are stored in a single Microsoft Access file. –limited to 2GB.
2. File geodatabases: stored in the system folder, and each file can be up to 1TB. –can be accessed by multiple operating systems, including Linux or Unix.
3. Enterprise (SDE) geodatabase: stores GIS data within a commercial relational database management system (RDBMS), such as Oracle or SQL Server. —designed to meet security and management needs for large data sets accessed by multiple users.

What is a geographic coordinate system (GCS)?

A geographic coordinate system (GCS) is a reference framework used to define the locations of points on the Earth’s surface. It is based on a three-dimensional spherical coordinate system and uses latitude and longitude to specify positions. Longitudes—measure horizontal angles east or west of the Prime Meridian (-180 to +180), and Latitudes are vertical angles above or below the equator (0 to -90, 0 to +90).

What is Map Projection?

A GCS is a three-dimensional coordinate system, but maps need to be flat. The conversion of the 3D map into a 2D map is called Map Projection.

Map Projection is the method of converting the Earth’s curved surface onto a flat map, allowing accurate representation and analysis. It ensures that spatial relationships, shapes, distances, and directions are preserved. Various types of map projections exist to achieve this, including:

1. Cylindrical Projection: Maps the Earth onto a cylinder, resulting in distortion at the poles but preserving direction and shapes along the equator.
2. Conic Projection: Projects the Earth onto a cone, best suited for mapping mid-latitude regions with minimal distortion along the parallels of latitude.
3. Planar Projection: Projects the Earth onto a flat plane tangent to the Earth’s surface, resulting in distortion away from the tangent point.
4. Azimuthal Projection: Projects the Earth onto a flat plane from a single point, preserving direction from the center of the projection but distorting other properties.

What are the differences between Project Tool and Define Projection

Project Tools	Define Projection
The tool operates on the x-y coordinates of a layer and converts them into a different coordinate system, resulting in a new feature class while keeping the original feature class unaffected.	Changes the projection system label of the feature class without modifying the internal coordinates.
The process of converting a layer from one coordinate system to another.	just labels the projection system
For accurate results, this operation is intended for properly georeferenced layers that are correctly positioned.	Designed for datasets with an Unknown coordinate system or mislabeled datasets that require correction in spatial positioning and alignment.

What are the differences between Geocoding and Geo-referencing?

Geocoding	Geo-referencing
Geocoding converts location descriptions into precise geographic coordinates on Earth’s surface.	Georeferencing, on the other hand, will align different types of geographic information to a known geographic coordinate system.
Geocoding involves the translation of various location descriptions, such as coordinate lists, addresses, place names, or lists of named objects/services/buildings without addresses, into corresponding geographic coordinates on Earth’s surface..	This allows a view of the respective information together with another already georeferenced layer of information.
The output is a geographic feature layer with an attribute table containing additional information.	The process includes data shifting, scaling, rotating, rectifying, etc.
Geocoding converts addresses or place names into map coordinates, allowing accurate marker placement on a map..	Georeferencing is a vital process that associates plain satellite or aerial images with map coordinates to enable their display on a map. It allows the overlaying of these images on street maps for better visualization. GIS software like ArcGIS or QGIS can be used to georeference un-referenced images or scanned maps and integrate them into Oracle Spatial. This enables accurate alignment and integration of imagery with spatial data, enhancing the overall mapping experience.
Geocoding in a spatial database involves representing places as point features with their names stored as attributes. For addresses, coordinates are computed using linear referencing, where start and end addresses are stored, and intermediate addresses are interpolated to calculate the corresponding coordinates.	Georeferencing is the process of taking a raster image or vector coverage, assigning it a coordinate system and coordinates, and translating, transforming, and warping/rubber-sheeting it into position relative to some other spatial data, such as survey locations, street intersections, etc.

To Get Familiar with GIS and Remote Sensing: Read our Blogs

What is a table?

A table is a data structure for storing multiple attributes about a location or an object. It is composed of rows, called records, and columns, called fields or attribute fields. An attribute table consists of information about features in a geographic data set.

• In a shapefile, the row is linked to the spatial feature in a separate file using a unique ID number called feature ID, or FID.
• In geodatabase, the file stores both the attributes and the x-y coordinates in the same data file, although the coordinates are not visible in the tables, and it uses an Object ID, or OID.

What is a Database Management System?

The system that are designed to store, manipulate, analyze, and protect tabular data of all kinds are Database Management Systems. There are various systems used to store data, such as INFO database (used for coverage), the dBase table (used for shapefiles), the Microsoft Access engine (used for personal geodatabases), and large-scale relational database management system (RDBMS), such as SQL Server (used for enterprise geodatabases). Three types of databases have traditionally been used:

Flat file database: stores rows of into in a text or binary file; simple but not efficient.

Hierarchical database: has multiple files, each of which contains different records and fields; parent tables can be linked to child hence defining the relationships.

Relational database: also has multiple tables stores as files, however, the relationships are not defined ahead of time; user defines can temporarily associate two tables if they share a common field. This association is called a join.

What is a Join?

In an RDBMS and in GIS, the tables are combined using a common field called a key, and this combining of two tables is called Join. The key field must be of the same data types in both tables. It merges information from different sources into a single dataset for analysis and visualization. For example, you can join population data with a city layer based on a common field like city name.

What is a Spatial Join?

In GIS, a spatial join combines data from different layers based on their spatial relationships. It uses the locations of features instead of common fields to determine matches, considering criteria like containment or proximity. This enables precise analysis and integration of spatial data.

What is a Map Overlay?

Map overlay combines two feature classes, merging their features and attributes to create a new feature class with comprehensive information.

What is a buffer?

Buffers are created to define areas that encompass a specific range of features. They can be generated for points, lines, and polygons, allowing for the identification of neighboring regions.

What is a Boolean Overlay?

The boolean overlay is similar to vector overlay, but it uses map algebra with Boolean rasters and operators.

What is Euclidean Distance?

The Euclidean Distance is a distance function that produces a raster in which each cell represents the shortest distance from a set of specified objects.

What is Interpolation?

Interpolation is a method to estimate the values in between the measurements. It takes measured values at points and distributes them across a raster.

What is a Reclassify function?

The Reclassify function changes the values of a raster according to a scheme designed by the user, such as classifying a slope map into three regions of low, medium, or high slope.

What are the components of GIS?

1. Hardware: fast-processing computer with high storage
2. GIS Software: produced and distributed by ESRI
3. Data Storage: data are voluminous so require high storage devices. Can be online too.
4. Information output hardware: Digitizer, scanner, printer etc. Fast-processing internet connection
5. GIS Data: Gathering data, assessing their accuracy, and maintaining them
6. GIS personnel: a trained person

What are the functionalities of GIS?

Varies widely. But providing the means to collect, manage, and analyze data to produce information for better decisions is the common goal and the strength of GIS.

1. Data entry: digitizing, scanning, text files, and the most common spatial data formats
2. Data management tools: building data sets, editing spatial feature and their attributes, managing to coordinate systems and projections
3. Thematic Mapping: symbolizing map features in different ways and combining layers for display
4. Data Analysis: exploring spatial relationships in and between map layers.
5. Map layout: creating soft and hard copy maps with tiles, scale bars, north arrows, and other maps elements

 

What are the new trends and directions in GIS?

ArcGIS Online, Web GIS, ArcGIS Pro, ESRI Story Maps, ArcGIS Story Maps, ArcGIS Map Journals.

What do GIS Professionals do?

1. Primary Data Providers: create base data. Surveyors, land-use planning professionals, photogrammetrists, remote sensing professionals, GPS experts
2. Application GIS: Geographers, hydrologists, land-use planners, business analysts, utility experts, statisticians, etc. who use GIS tools and skills to make their work efficient, productive, and valuable.
3. GIS Developer: skilled software and hardware engineers—build and maintain GIS software
4. GIS Database Distributor: experts in computer science and networking, Internet protocols, and/or database management systems—set up and maintain the complex server and network systems that allow data services, Server GIS, and Enterprise to operate.