Use symbolic names for projections

src/command-line-parser.cpp

@@ -14,6 +14,7 @@
 #include "logging.hpp"
 #include "options.hpp"
 #include "pgsql.hpp"
+#include "projection.hpp"
 #include "reprojection.hpp"
 #include "util.hpp"
 #include "version.hpp"
@@ -244,7 +245,7 @@ void check_options_expire(options_t *options) {
     }
 
     if (options->expire_tiles_zoom != 0 &&
-        options->projection->target_srs() != 3857) {
+        options->projection->target_srs() != PROJ_SPHERE_MERC) {
         log_warn("Expire has been enabled (with -e or --expire-tiles) but "
                  "target SRS is not Mercator (EPSG:3857). Expire disabled!");
         options->expire_tiles_zoom = 0;

src/expire-tiles.cpp

@@ -28,6 +28,7 @@
 #include "format.hpp"
 #include "geom-functions.hpp"
 #include "options.hpp"
+#include "projection.hpp"
 #include "reprojection.hpp"
 #include "table.hpp"
 #include "tile.hpp"
@@ -146,7 +147,7 @@ void expire_tiles::from_geometry(geom::geometry_t const &geom,
 void expire_tiles::from_geometry_if_3857(geom::geometry_t const &geom,
                                          expire_config_t const &expire_config)
 {
-    if (geom.srid() == 3857) {
+    if (geom.srid() == PROJ_SPHERE_MERC) {
         from_geometry(geom, expire_config);
     }
 }

src/flex-lua-geom.cpp

@@ -12,6 +12,7 @@
 #include "geom-functions.hpp"
 #include "geom-pole-of-inaccessibility.hpp"
 #include "lua-utils.hpp"
+#include "projection.hpp"
 
 #include <lua.hpp>
 
@@ -73,7 +74,7 @@ int geom_spherical_area(lua_State *lua_state)
 {
     auto const *const input_geometry = unpack_geometry(lua_state);
 
-    if (input_geometry->srid() != 4326) {
+    if (input_geometry->srid() != PROJ_LATLONG) {
         throw std::runtime_error{"Can only calculate spherical area for "
                                  "geometries in WGS84 (4326) coordinates."};
     }
@@ -282,7 +283,7 @@ int geom_transform(lua_State *lua_state)
     auto const srid = static_cast<int>(luaL_checkinteger(lua_state, 2));
 
     try {
-        if (input_geometry->srid() != 4326) {
+        if (input_geometry->srid() != PROJ_LATLONG) {
             throw std::runtime_error{
                 "Can not transform already transformed geometry."};
         }

src/flex-lua-table.cpp

@@ -16,6 +16,7 @@
 #include "lua-utils.hpp"
 #include "output-flex.hpp"
 #include "pgsql-capabilities.hpp"
+#include "projection.hpp"
 #include "util.hpp"
 
 #include <lua.hpp>
@@ -219,7 +220,7 @@ void parse_and_set_expire_options(lua_State *lua_state,
         return;
     }
 
-    if (!column->is_geometry_column() || column->srid() != 3857) {
+    if (!column->is_geometry_column() || column->srid() != PROJ_SPHERE_MERC) {
         throw std::runtime_error{"Expire only allowed for geometry"
                                  " columns in Web Mercator projection."};
     }

src/flex-table-column.cpp

@@ -11,6 +11,7 @@
 
 #include "format.hpp"
 #include "pgsql-capabilities.hpp"
+#include "projection.hpp"
 #include "util.hpp"
 
 #include <cassert>
@@ -105,12 +106,12 @@ void flex_table_column_t::set_projection(char const *projection)
     auto const proj = lowercase(projection);
 
     if (proj == "merc" || proj == "mercator") {
-        m_srid = 3857;
+        m_srid = PROJ_SPHERE_MERC;
         return;
     }
 
     if (proj == "latlong" || proj == "latlon" || proj == "wgs84") {
-        m_srid = 4326;
+        m_srid = PROJ_LATLONG;
         return;
     }
 
@@ -197,7 +198,7 @@ std::string flex_table_column_t::sql_create() const
 void flex_table_column_t::add_expire(expire_config_t const &config)
 {
     assert(is_geometry_column());
-    assert(srid() == 3857);
+    assert(srid() == PROJ_SPHERE_MERC);
     m_expires.push_back(config);
 }
 

src/flex-table-column.hpp

@@ -13,6 +13,7 @@
 #include "expire-config.hpp"
 #include "expire-tiles.hpp"
 #include "geom.hpp"
+#include "projection.hpp"
 
 #include <cassert>
 #include <cstdint>
@@ -99,7 +100,7 @@ class flex_table_column_t
     bool needs_isvalid() const noexcept
     {
         assert(is_geometry_column());
-        return !m_create_only && m_srid != 4326 &&
+        return !m_create_only && m_srid != PROJ_LATLONG &&
                m_type != table_column_type::point;
     }
 
@@ -158,7 +159,7 @@ class flex_table_column_t
     /**
      * For geometry columns only: The projection SRID. Default is web mercator.
      */
-    int m_srid = 3857;
+    int m_srid = PROJ_SPHERE_MERC;
 
     /// NOT NULL constraint
     bool m_not_null = false;

src/flex-table.hpp

@@ -14,6 +14,7 @@
 #include "flex-index.hpp"
 #include "flex-table-column.hpp"
 #include "pgsql.hpp"
+#include "projection.hpp"
 #include "reprojection.hpp"
 #include "thread-pool.hpp"
 #include "util.hpp"
@@ -145,7 +146,7 @@ class flex_table_t
 
     int srid() const noexcept
     {
-        return has_geom_column() ? geom_column().srid() : 4326;
+        return has_geom_column() ? geom_column().srid() : PROJ_LATLONG;
     }
 
     std::string build_sql_prepare_get_wkb() const;

src/gen/gen-rivers.cpp

@@ -14,6 +14,7 @@
 #include "logging.hpp"
 #include "params.hpp"
 #include "pgsql.hpp"
+#include "projection.hpp"
 #include "util.hpp"
 #include "wkb.hpp"
 
@@ -341,7 +342,7 @@ SELECT "{id_column}", "{width_column}", "{name_column}", "{geom_column}"
     timer(m_timer_write).start();
     connection().exec("BEGIN");
     for (auto &edge : edges) {
-        geom::geometry_t const geom{std::move(edge.points), 3857};
+        geom::geometry_t const geom{std::move(edge.points), PROJ_SPHERE_MERC};
         auto const wkb = geom_to_ewkb(geom);
         connection().exec_prepared("ins", edge.id, edge.width,
                                    get_name(names, edge.id), binary_param(wkb));

src/gen/raster.hpp

@@ -10,6 +10,8 @@
  * For a full list of authors see the git log.
  */
 
+#include "projection.hpp"
+
 #include <cstdint>
 #include <string>
 
@@ -41,7 +43,7 @@ struct wkb_raster_header
     double ipY = 0.0;
     double skewX = 0.0;
     double skewY = 0.0;
-    int32_t srid = 3857;
+    int32_t srid = PROJ_SPHERE_MERC;
     uint16_t width = 0;
     uint16_t height = 0;
 };

src/gen/tracer.cpp

@@ -11,6 +11,7 @@
 
 #include "canvas.hpp"
 #include "geom-boost-adaptor.hpp"
+#include "projection.hpp"
 #include "tile.hpp"
 
 #include <cassert>
@@ -114,7 +115,7 @@ tracer_t::build_geometries(tile_t const &tile, potrace_path_t const *plist,
             m_num_points += ring.size();
 
             if (path->sign == '+') {
-                geometries.emplace_back(geom::polygon_t{}, 3857)
+                geometries.emplace_back(geom::polygon_t{}, PROJ_SPHERE_MERC)
                     .get<geom::polygon_t>()
                     .outer() = std::move(ring);
             } else {

src/geom-functions.cpp

@@ -11,6 +11,7 @@
 
 #include "geom-boost-adaptor.hpp"
 #include "overloaded.hpp"
+#include "projection.hpp"
 
 #include <algorithm>
 #include <cmath>
@@ -228,7 +229,7 @@ class transform_visitor
 void transform(geometry_t *output, geometry_t const &input,
                reprojection const &reprojection)
 {
-    assert(input.srid() == 4326);
+    assert(input.srid() == PROJ_LATLONG);
 
     set_to_same_type(output, input);
     output->set_srid(reprojection.target_srs());
@@ -385,7 +386,7 @@ double spherical_area(polygon_t const &geom)
 
 double spherical_area(geometry_t const &geom)
 {
-    assert(geom.srid() == 4326);
+    assert(geom.srid() == PROJ_LATLONG);
 
     return std::abs(geom.visit(overloaded{
         [&](geom::nullgeom_t const & /*input*/) { return 0.0; },

src/geom.hpp

@@ -16,6 +16,8 @@
  * Basic geometry types and functions.
  */
 
+#include "projection.hpp"
+
 #include <osmium/osm/location.hpp>
 
 #include <algorithm>
@@ -274,31 +276,33 @@ class geometry_t
 
     // point_t is small and trivially copyable, no move needed like for the
     // other constructors.
-    constexpr explicit geometry_t(point_t geom, int srid = 4326)
+    constexpr explicit geometry_t(point_t geom, int srid = PROJ_LATLONG)
     : m_geom(geom), m_srid(srid)
     {}
 
-    constexpr explicit geometry_t(linestring_t &&geom, int srid = 4326)
+    constexpr explicit geometry_t(linestring_t &&geom, int srid = PROJ_LATLONG)
     : m_geom(std::move(geom)), m_srid(srid)
     {}
 
-    constexpr explicit geometry_t(polygon_t &&geom, int srid = 4326)
+    constexpr explicit geometry_t(polygon_t &&geom, int srid = PROJ_LATLONG)
     : m_geom(std::move(geom)), m_srid(srid)
     {}
 
-    constexpr explicit geometry_t(multipoint_t &&geom, int srid = 4326)
+    constexpr explicit geometry_t(multipoint_t &&geom, int srid = PROJ_LATLONG)
     : m_geom(std::move(geom)), m_srid(srid)
     {}
 
-    constexpr explicit geometry_t(multilinestring_t &&geom, int srid = 4326)
+    constexpr explicit geometry_t(multilinestring_t &&geom,
+                                  int srid = PROJ_LATLONG)
     : m_geom(std::move(geom)), m_srid(srid)
     {}
 
-    constexpr explicit geometry_t(multipolygon_t &&geom, int srid = 4326)
+    constexpr explicit geometry_t(multipolygon_t &&geom,
+                                  int srid = PROJ_LATLONG)
     : m_geom(std::move(geom)), m_srid(srid)
     {}
 
-    constexpr explicit geometry_t(collection_t &&geom, int srid = 4326)
+    constexpr explicit geometry_t(collection_t &&geom, int srid = PROJ_LATLONG)
     : m_geom(std::move(geom)), m_srid(srid)
     {}
 
@@ -397,7 +401,7 @@ class geometry_t
                  multilinestring_t, multipolygon_t, collection_t>
         m_geom = nullgeom_t{};
 
-    int m_srid = 4326;
+    int m_srid = PROJ_LATLONG;
 
 }; // class geometry_t
 

src/locator.cpp

@@ -16,6 +16,7 @@
 #include "overloaded.hpp"
 #include "pgsql-capabilities.hpp"
 #include "pgsql.hpp"
+#include "projection.hpp"
 #include "wkb.hpp"
 
 #include <iterator>
@@ -63,7 +64,7 @@ void locator_t::add_regions(pg_conn_t const &db_connection,
         std::string const name = result.get_value(n, 0);
         auto geometry = ewkb_to_geom(util::decode_hex(result.get(n, 1)));
 
-        if (geometry.srid() == 4326) {
+        if (geometry.srid() == PROJ_LATLONG) {
             add_region(name, geometry);
         } else {
             log_warn("Ignoring locator geometry that is not in WGS84 (4326)");

src/output-flex.cpp

@@ -33,6 +33,7 @@
 #include "osmtypes.hpp"
 #include "pgsql-capabilities.hpp"
 #include "pgsql.hpp"
+#include "projection.hpp"
 #include "properties.hpp"
 #include "reprojection.hpp"
 #include "thread-pool.hpp"
@@ -1191,8 +1192,9 @@ output_flex_t::output_flex_t(output_flex_t const *other,
     }
 
     for (auto &expire_output : *m_expire_outputs) {
-        m_expire_tiles.emplace_back(expire_output.maxzoom(),
-                                    reprojection::create_projection(3857));
+        m_expire_tiles.emplace_back(
+            expire_output.maxzoom(),
+            reprojection::create_projection(PROJ_SPHERE_MERC));
     }
 }
 
@@ -1235,7 +1237,8 @@ output_flex_t::output_flex_t(std::shared_ptr<middle_query_t> const &mid,
         eo.set_maxzoom(options.expire_tiles_zoom);
 
         for (auto &table : *m_tables) {
-            if (table.has_geom_column() && table.geom_column().srid() == 3857) {
+            if (table.has_geom_column() &&
+                table.geom_column().srid() == PROJ_SPHERE_MERC) {
                 expire_config_t config{};
                 config.expire_output = m_expire_outputs->size() - 1;
                 if (options.expire_tiles_max_bbox > 0.0) {
@@ -1255,8 +1258,9 @@ output_flex_t::output_flex_t(std::shared_ptr<middle_query_t> const &mid,
     }
 
     for (auto &expire_output : *m_expire_outputs) {
-        m_expire_tiles.emplace_back(expire_output.maxzoom(),
-                                    reprojection::create_projection(3857));
+        m_expire_tiles.emplace_back(
+            expire_output.maxzoom(),
+            reprojection::create_projection(PROJ_SPHERE_MERC));
     }
 
     create_expire_tables(*m_expire_outputs, get_options()->connection_params);

src/output-pgsql.cpp

@@ -38,6 +38,7 @@
 #include "osmtypes.hpp"
 #include "output-pgsql.hpp"
 #include "pgsql.hpp"
+#include "projection.hpp"
 #include "reprojection.hpp"
 #include "taginfo-impl.hpp"
 #include "tagtransform.hpp"
@@ -51,7 +52,7 @@ double calculate_area(bool reproject_area, geom::geometry_t const &geom4326,
                       geom::geometry_t const &projected_geom)
 {
     static thread_local auto const proj3857 =
-        reprojection::create_projection(3857);
+        reprojection::create_projection(PROJ_SPHERE_MERC);
 
     if (reproject_area) {
         auto const ogeom = geom::transform(geom4326, *proj3857);

src/projection.hpp

@@ -0,0 +1,16 @@
+#ifndef OSM2PGSQL_PROJECTION_HPP
+#define OSM2PGSQL_PROJECTION_HPP
+
+/**
+ * SPDX-License-Identifier: GPL-2.0-or-later
+ *
+ * This file is part of osm2pgsql (https://osm2pgsql.org/).
+ *
+ * Copyright (C) 2006-2025 by the osm2pgsql developer community.
+ * For a full list of authors see the git log.
+ */
+
+constexpr int PROJ_LATLONG = 4326;
+constexpr int PROJ_SPHERE_MERC = 3857;
+
+#endif // OSM2PGSQL_PROJECTION_HPP

src/reprojection.hpp

@@ -17,16 +17,11 @@
  */
 
 #include "geom.hpp"
+#include "projection.hpp"
 
 #include <memory>
 #include <string>
 
-enum Projection
-{
-    PROJ_LATLONG = 4326,
-    PROJ_SPHERE_MERC = 3857
-};
-
 /**
  * Virtual base class used for projecting OSM WGS84 coordinates into a
  * different coordinate system. Most commonly this will be used to convert