Pros of PROJ

• Specialized focus on coordinate transformations and map projections
• Lightweight and efficient for geospatial operations
• Widely used in GIS applications and supported by many geospatial libraries

Cons of PROJ

• Limited scope compared to CGAL's broader computational geometry offerings
• Less suitable for complex geometric algorithms beyond coordinate transformations
• Smaller community and fewer contributors compared to CGAL

Code Comparison

PROJ (coordinate transformation):

PJ *P;
P = proj_create_crs_to_crs(PJ_DEFAULT_CTX, "EPSG:4326", "EPSG:3857", NULL);
proj_trans(P, PJ_FWD, coord);
proj_destroy(P);

CGAL (geometric computation):

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
K::Point_2 p(1, 1), q(10, 10);
double distance = CGAL::squared_distance(p, q);

PROJ is more focused on coordinate transformations and map projections, making it ideal for geospatial applications. CGAL offers a broader range of computational geometry algorithms, suitable for more complex geometric computations. PROJ is lighter and more efficient for specific geospatial tasks, while CGAL provides a comprehensive toolkit for various geometric problems.

Pros of GEOS

• Simpler API and easier to use for basic geometric operations
• Faster performance for certain operations, especially with large datasets
• Better support for GIS-specific functionality and coordinate systems

Cons of GEOS

• Less comprehensive feature set compared to CGAL
• Limited support for higher-dimensional geometry and advanced algorithms
• Fewer options for exact arithmetic and precision control

Code Comparison

GEOS example (C++):

#include <geos/geom/Geometry.h>
#include <geos/geom/GeometryFactory.h>
#include <geos/io/WKTReader.h>

geos::geom::GeometryFactory::Ptr factory = geos::geom::GeometryFactory::create();
geos::io::WKTReader reader(*factory);
std::unique_ptr<geos::geom::Geometry> geom(reader.read("POINT(0 0)"));

CGAL example (C++):

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Point_2.h>

typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Point_2<K> Point_2;

Point_2 p(0, 0);

Both GEOS and CGAL are powerful computational geometry libraries, but they cater to different use cases. GEOS is more focused on GIS applications and simpler geometric operations, while CGAL offers a broader range of algorithms and more precise computations. The choice between them depends on the specific requirements of your project.

Pros of QGIS

• More user-friendly with a graphical interface for GIS operations
• Broader functionality for geospatial analysis and cartography
• Larger community and more frequent updates

Cons of QGIS

• Slower performance for complex computational geometry tasks
• Less specialized for advanced geometric algorithms
• Steeper learning curve for developers due to its size and complexity

Code Comparison

CGAL (C++):

#include <CGAL/Exact_predicates_inexact_constructions_kernel.h>
#include <CGAL/Delaunay_triangulation_2.h>

typedef CGAL::Exact_predicates_inexact_constructions_kernel K;
typedef CGAL::Delaunay_triangulation_2<K> Triangulation;
Triangulation t;

QGIS (Python):

from qgis.core import QgsVectorLayer, QgsProject

layer = QgsVectorLayer("Point", "points", "memory")
QgsProject.instance().addMapLayer(layer)

CGAL focuses on computational geometry algorithms, providing efficient and robust implementations. It's ideal for developers working on geometric problems and requires C++ expertise.

QGIS is a comprehensive GIS software with a user-friendly interface, suitable for a wide range of geospatial tasks. It offers Python scripting for customization and plugin development, making it accessible to both users and developers.