Land use land cover (LULC) mapping is essential for understanding environmental changes and land management. Traditional manual LULC mapping involves expert interpretation of satellite images and field surveys, ensuring high accuracy but requiring significant time and effort. In contrast, modern techniques utilize the Google Earth Engine (GEE) combined with artificial intelligence (AI) and machine learning (ML) to automate and scale the mapping process. This approach leverages cloud-based processing and advanced algorithms to quickly classify large areas with improved consistency and accuracy. The following sections delve into these methodologies and compare their processes, advantages, and limitations.
For Manual Method
First, you start by collecting satellite images from the USGS (United States Geological Survey). For this project, data from the Landsat 8 and 9 satellites, which are well known for capturing detailed images of the Earth's surface, were chosen. After selecting the right satellite images, the next step is to download these data to your computer.
Once the data, are available, they need to be preprocessed. Preprocessing involves getting the data ready for analysis, which might include cleaning up the images, correcting any distortions, and ensuring that everything is lined up correctly. After preprocessing, the focus was narrowed to a specific area of interest (AOI) by using ArcGIS software. This means you will be working with just the part of the satellite image that covers the area you are interested in studying.
The next important step is selecting training sets. This involves manually identifying and marking different types of land cover, such as forests, water bodies, or urban areas, in an AOI. These training sets are used in the supervised classification process. Here, a machine learning algorithm, specifically the maximum likelihood algorithm, is applied to the entire image. The training sets were used to categorize every part of the AOI into different land cover types.
After running the classification, an output map that shows the LULC of your area is obtained. This map is initially in raster format, which is grid-based. For further analysis, these raster data were converted into vector format, where the land cover types are represented as polygons.
Next, the area covered by each type of land cover was calculated. This helps you understand the extent of different land covers within your AOI. To ensure the results are reliable, an accuracy assessment. This involves comparing the classified map with actual ground data or higher-resolution images to determine how accurate the classification is.
Finally, if you are interested in how the land cover has changed over time, you can perform a change detection analysis. This step involved comparing the current LULC map with maps from previous years to identify any significant changes, such as deforestation, urban expansion, or changes in water bodies.
This entire process (shown in Fig. 1.2), from data collection to change detection, provides a comprehensive way to map and analyze the land use and cover of an area, which is crucial for environmental management, urban planning, and resource monitoring.
Generated using the Google Earth Engine with AI and ML
The process of creating a land use/land cover (LULC) map using artificial intelligence (AI) methods begins with utilizing the Google Earth Engine (GE) to analyze Sentinel-2 satellite imagery. These high-resolution data are imported into the platform, where artificial intelligence and machine learning techniques are applied to classify the land into different cover types. The classification process involved training models using JavaScript and Python, to ensure that the algorithms accurately categorized the land cover. Once the classification was complete, the area covered by each land type was calculated, and an accuracy assessment was subsequently performed to validate the results. Finally, the LULC map, which visually represents the different land cover types, was exported for further use. This approach leverages advanced AI techniques to create precise and efficient land cover maps.
Advantages and Limitations of Both Methods
Advantages:
- ArcGIS with Manually Trained Data
- High accuracy due to user knowledge and local expertise.
- Customizable classification tailored to specific needs.
- Detailed control over the classification process.
- Ideal for small or medium-sized areas requiring precise, hands-on control.
- This approach is effective for temporal analysis with high accuracy for specific time periods.
- GEE with AI-Generated Scripts:
- This approach is highly scalable and suitable for large-scale projects, including global analyses.
- AI-driven automation is effective at reducing the time required for LULC mapping.
- Consistent classification across large datasets reduces subjectivity.
- The internet is accessible and offers free access to extensive satellite imagery and tools.
- This simplifies the classification process, decreasing the need for deep GIS expertise.
- This approach is useful for dynamic mapping and temporal analysis, allowing for near real-time data use.
Disadvantages:
- ArcGIS with Manually Trained Data
- Subjectivity in accuracy due to dependence on user expertise can lead to potential biases.
- This process is time consuming and labor-intensive, making it impractical for large-scale projects.
- Limited scalability and difficulty extending to larger areas without additional effort.
- Low automation, limiting efficiency for large datasets or repetitive tasks.
- The steep learning curve for users unfamiliar with a GIS makes it less accessible.
- GEE with AI-Generated Scripts:
- The training data quality is dependent upon the training data quality, and inaccuracies may occur if the data are not representative.
- The black-box nature of AI models limits the interpretability of the results.
- There is limited customization compared to manual classification methods.
- AI and machine learning expertise are needed, which may not be accessible to all users.
- Internet dependency, with potential limitations in areas with poor connectivity.
- Usage quotas and computational limits, particularly for free-tier users.
- Ongoing maintenance, as required for AI models, may need retraining with new data.