Generalising Alt-Az projection

.gitignore

@@ -1,5 +1,8 @@
 *.pyc
 
+#chart configurations I use to debug
+test/
+
 # Distribution / packaging
 develop-eggs/
 dist/

README.md

@@ -209,6 +209,7 @@ The following settings can be included in a `StarCharter` configuration file:
 * `grid_col` - Colour to use when drawing grid of RA/Dec lines
 * `label_ecliptic` - Boolean (0 or 1) indicating whether to label the months along the ecliptic, showing the Sun's annual progress
 * `label_font_size_scaling` - Scaling factor to be applied to the font size of all star and DSO labels (default 1.0)
+* `label_meridian` Boolean (0 or 1) indicating whether to label declination lines multiple of 10 degrees along the vernal meridian 
 * `language` - The language used for the constellation names. Either "english" or "french".
 * `mag_alpha` - The multiplicative scaling factor to apply to the radii of stars differing in magnitude by one <mag_step>
 * `mag_max` - Used to regulate the size of stars. A star of this magnitude is drawn with size mag_size_norm. Also, this is the brightest magnitude of star which is shown in the magnitude key below the chart.
@@ -220,6 +221,7 @@ The following settings can be included in a `StarCharter` configuration file:
 * `maximum_dso_label_count` - The maximum number of deep sky objects which may be labelled
 * `maximum_star_count` - The maximum number of stars to draw. If this is exceeded, only the brightest stars are shown.
 * `maximum_star_label_count` - The maximum number of stars which may be labelled
+* `meridian_col` - Colour to use when drawing a line along the vernal meridian
 * `messier_only` - Boolean (0 or 1) indicating whether we plot only Messier objects, and no other deep sky objects
 * `must_show_all_ephemeris_labels` - Boolean (0 or 1) indicating whether we show all ephemeris text labels, even if they collide with other text.
 * `output_filename` - The target filename for the star chart. The file type (svg, png, eps or pdf) is inferred from the file extension.
@@ -229,6 +231,7 @@ The following settings can be included in a `StarCharter` configuration file:
 * `plot_equator` - Boolean (0 or 1) indicating whether to draw a line along the equator
 * `plot_galactic_plane` - Boolean (0 or 1) indicating whether to draw a line along the galactic plane
 * `plot_galaxy_map` - Boolean (0 or 1) indicating whether to draw a shaded map of the Milky Way behind the star chart
+* `plot_meridian` - Boolean (0 or 1) indicating whether we plot the vernal meridian
 * `plot_stars` - Boolean (0 or 1) indicating whether we plot any stars
 * `position_angle` - The position angle of the plot - i.e. the tilt of north, counter-clockwise from up, at the centre of the plot
 * `projection` - Select projection to use. Set to either flat, peters, gnomonic, sphere or alt_az
@@ -244,8 +247,26 @@ The following settings can be included in a `StarCharter` configuration file:
 * `star_mag_labels` - Boolean (0 or 1) indicating whether we label the magnitudes of stars
 * `star_names` - Boolean (0 or 1) indicating whether we label the English names of stars
 * `star_variable_labels` - Boolean (0 or 1) indicating whether we label the variable-star designations of stars, e.g. V337_Car
+* `dec_ticks_on_round_edge` - Boolean (o or 1) indicating whether lines of constant declination (or galactic latitude) put a tick on the round edge of an Alt_Az chart
+* `ra_ticks_on_round_edge` - Boolean (o or 1) indicating whether lines of constant right ascension (or galactic longitude) put a tick on the round edge of an Alt_Az chart
 * `title` - The heading to write at the top of the star chart
 * `width` - The width of the star chart, in cm
 * `x_label_slant` - A slant to apply to all labels on the horizontal axes
 * `y_label_slant` - A slant to apply to all labels on the vertical axes
 * `zodiacal_only` - Boolean (0 or 1) indicating whether we plot only the zodiacal constellations
+
+# Changelog
+
+## Functionalities
+
+* Extended `alt_az` plotting to draw charts of arbitrary (<360°) angular width. E.G., this is useful to plot a chart of all stars you can see throughout the year
+* Implemented ticks on round edge of the chart in `alt_az` mode, with the possibility to choose whether RA, Dec or both lines put ticks on it
+* Possibility to plot the vernal meridian, with the option to put a tick on it every 10° of declination
+
+## New configuration parameters
+
+* `label_meridian`
+* `meridian_col`
+* `plot_meridian`
+* `dec_ticks_on_round_edge`
+* `ra_ticks_on_round_edge`

src/astroGraphics/constellations.c

@@ -66,7 +66,7 @@ void plot_constellation_boundaries(chart_config *s, line_drawer *ld) {
 
     // Set up line-drawing class
     ld_pen_up(ld, GSL_NAN, GSL_NAN, NULL, 1);
-    ld_label(ld, NULL, 1, 1);
+    ld_label(ld, NULL, 1, 1, 1);
 
     // Open file defining the celestial coordinates of the constellation boundaries
     file = fopen(SRCDIR "../data/constellations/downloads/boundaries.dat", "r");

src/astroGraphics/ephemeris.c

@@ -518,7 +518,7 @@ void plot_ephemeris(chart_config *s, line_drawer *ld, cairo_page *page, int trac
     // Set line colour
     ld_pen_up(ld, GSL_NAN, GSL_NAN, NULL, 1);
     cairo_set_source_rgb(s->cairo_draw, s->ephemeris_col.red, s->ephemeris_col.grn, s->ephemeris_col.blu);
-    ld_label(ld, NULL, 1, 1);
+    ld_label(ld, NULL, 1, 1, 1);
 
     // Loop over the points in the ephemeris, and draw a line across the star chart
     const ephemeris *e = &s->ephemeris_data[trace_num];
@@ -591,7 +591,7 @@ void plot_ephemeris(chart_config *s, line_drawer *ld, cairo_page *page, int trac
 
             // Draw tick mark
             ld_pen_up(ld, GSL_NAN, GSL_NAN, NULL, 1);
-            ld_label(ld, NULL, 1, 1);
+            ld_label(ld, NULL, 1, 1, 1);
             ld_point(ld, x + graph_coords_tick_len * sin(theta), y - graph_coords_tick_len * cos(theta), NULL);
             ld_point(ld, x - graph_coords_tick_len * sin(theta), y + graph_coords_tick_len * cos(theta), NULL);
             ld_pen_up(ld, GSL_NAN, GSL_NAN, NULL, 1);
@@ -894,4 +894,4 @@ double draw_ephemeris_table(chart_config *s, double legend_y_pos, int draw_outpu
     }
 
     return legend_y_pos;
-}
+}

src/astroGraphics/greatCircles.c

@@ -61,7 +61,7 @@ static void plot_great_circle(double ra0, double dec0, chart_config *s, line_dra
     dec0 = dec0 * M_PI / 180;
     ld_pen_up(ld, GSL_NAN, GSL_NAN, NULL, 1);
     for (i = 0; i <= N_SAMPLES; i++) {
-        const double l = 2 * M_PI * ((double) i) / N_SAMPLES;
+        const double l = 2 * M_PI * ((double) i) / (N_SAMPLES-1);
         double a[3] = {cos(l), sin(l), 0.};
         double ra, dec, x, y;
 
@@ -97,6 +97,56 @@ static void plot_great_circle(double ra0, double dec0, chart_config *s, line_dra
         }
 }
 
+//small modification to print half circle, useful for meridians.
+
+static void plot_great_half_circle(double ra0, double dec0, chart_config *s, line_drawer *ld,
+                              cairo_page *page, int n_labels, gc_label *labels, colour colour) {
+    int i;
+    ra0 = ra0 * M_PI / 180;
+    dec0 = dec0 * M_PI / 180;
+    ld_pen_up(ld, GSL_NAN, GSL_NAN, NULL, 1);
+    for (i = 0; i <= N_SAMPLES; i++) {
+        const double l = M_PI * ((double) i) / (N_SAMPLES-1);
+        double a[3] = {cos(l), sin(l), 0.};
+        double ra, dec, x, y;
+
+        rotate_xz(a, a, dec0 - (M_PI / 2));
+        rotate_xy(a, a, ra0);
+
+        dec = asin(a[2]);
+        ra = atan2(a[1], a[0]);
+        plane_project(&x, &y, s, ra, dec, 0);
+        ld_point(ld, x, y, NULL);
+    }
+    ld_pen_up(ld, GSL_NAN, GSL_NAN, NULL, 1);
+
+    if (n_labels)
+        for (i = 0; i < n_labels; i++) {
+            const double l = M_PI*(labels[i].xpos) / 180;
+            double a[3] = {cos(l), sin(l), 0.};
+            double ra, dec, x, y, xtemp, ytemp;
+
+            rotate_xz(a, a, dec0 - (M_PI / 2));
+            rotate_xy(a, a, ra0);
+
+            dec = asin(a[2]);
+            ra = atan2(a[1], a[0]);
+            plane_project(&x, &y, s, ra, dec, 0);
+	    plane_project(&xtemp, &ytemp, s, ra-0.0000000001/(dec-M_PI/2), dec, 0);
+	    //very, VERY brutal 1st order approximation
+            ld_point(ld, x+(xtemp-x)/sqrt((x-xtemp)*(x-xtemp)+(y-ytemp)*(y-ytemp))/50, y+(ytemp-y)/sqrt(((x-xtemp)*(x-xtemp))+((y-ytemp)*(y-ytemp)))/50, NULL);
+            ld_point(ld, x, y, NULL);
+	    plane_project(&xtemp, &ytemp, s, ra+0.000000001/(dec-M_PI/2), dec, 0);
+	    ld_point(ld, x+(xtemp-x)/sqrt((x-xtemp)*(x-xtemp)+(y-ytemp)*(y-ytemp))/50, y+(ytemp-y)/sqrt(((x-xtemp)*(x-xtemp))+((y-ytemp)*(y-ytemp)))/50, NULL);
+            ld_pen_up(ld, GSL_NAN, GSL_NAN, NULL, 1);
+	    plane_project(&xtemp, &ytemp, s, ra+0.1/(dec-M_PI/2), dec, 0);
+
+            chart_label_buffer(page, s, colour, labels[i].label,
+                               &(label_position) {x+(xtemp-x)/sqrt(((x-xtemp)*(x-xtemp))+((y-ytemp)*(y-ytemp)))/25, y+(ytemp-y)/sqrt(((x-xtemp)*(x-xtemp))+((y-ytemp)*(y-ytemp)))/25, 0, 0, -1}, 1,
+                               0, 1, 2.0, 1, 0, 0, -0.5);
+        }
+}
+
 //! plot_equator - Draw a line along the celestial equator
 //! \param s - A <chart_config> structure defining the properties of the star chart to be drawn.
 //! \param ld - A <line_drawer> structure used to draw lines on a cairo surface.
@@ -110,6 +160,34 @@ void plot_equator(chart_config *s, line_drawer *ld, cairo_page *page) {
 
     plot_great_circle(0, 90, s, ld, page, 0, NULL, s->equator_col);
 }
+// plots RA=0 meridian
+void plot_meridian(chart_config *s, line_drawer *ld, cairo_page *page) {
+    gc_label labels[17] = {{"-80", 10},
+                           {"-70", 20},
+                           {"-60", 30},
+                           {"-50", 40},
+                           {"-40", 50},
+                           {"-30", 60},
+                           {"-20", 70},
+                           {"-10", 80},
+                           {"0", 90},
+                           {"10", 100},
+                           {"20", 110},
+                           {"30", 120},
+			   {"40", 130},
+			   {"50", 140},
+			   {"60", 150},
+			   {"70", 160},
+			   {"80", 170},
+    };
+    // Set line colour
+    ld_pen_up(ld, GSL_NAN, GSL_NAN, NULL, 1);
+    cairo_set_source_rgb(s->cairo_draw, s->meridian_col.red, s->meridian_col.grn, s->meridian_col.blu);
+    cairo_set_line_width(s->cairo_draw, s->great_circle_line_width);
+
+    plot_great_half_circle(-90, 0, s, ld, page, s->label_meridian ? 17 : 0, labels,
+                      s->meridian_col);
+}
 
 //! plot_galactic_plane - Draw a line along the plane of the Milky Way
 //! \param s - A <chart_config> structure defining the properties of the star chart to be drawn.
@@ -161,7 +239,7 @@ void plot_ecliptic(chart_config *s, line_drawer *ld, cairo_page *page) {
 //! \param legend_y_pos - The vertical pixel position of the top of the next legend to go under the star chart.
 
 double draw_great_circle_key(chart_config *s, double legend_y_pos) {
-    const int N = (s->plot_equator != 0) + (s->plot_ecliptic != 0) + (s->plot_galactic_plane != 0);
+    const int N = (s->plot_meridian != 0) + (s->plot_equator != 0) + (s->plot_ecliptic != 0) + (s->plot_galactic_plane != 0);
     const double w_left = 0.4; // The left margin
     const double w_item = 4.2 * s->font_size; // The width of each legend item (cm)
 
@@ -188,12 +266,12 @@ double draw_great_circle_key(chart_config *s, double legend_y_pos) {
     // Reset font weight
     cairo_select_font_face(s->cairo_draw, s->font_family, CAIRO_FONT_SLANT_NORMAL, CAIRO_FONT_WEIGHT_NORMAL);
 
-    // Draw item on legend showing the colour of the equator
+     // Draw item on legend showing the colour of the meridian
     if (s->plot_equator != 0) {
-        const char *label = "The Equator";
+        const char *label = "Vernal Meridian";
 
         // Draw a line in the right colour
-        cairo_set_source_rgb(s->cairo_draw, s->equator_col.red, s->equator_col.grn, s->equator_col.blu);
+        cairo_set_source_rgb(s->cairo_draw, s->meridian_col.red, s->meridian_col.grn, s->meridian_col.blu);
         cairo_new_path(s->cairo_draw);
         cairo_move_to(s->cairo_draw, x * s->cm, y1 * s->cm);
         cairo_line_to(s->cairo_draw, (x + size) * s->cm, y1 * s->cm);
@@ -216,6 +294,30 @@ double draw_great_circle_key(chart_config *s, double legend_y_pos) {
     if (s->plot_ecliptic != 0) {
         const char *label = "Ecliptic Plane";
 
+   // Draw item on legend showing the colour of the equator
+    if (s->plot_equator != 0) {
+        const char *label = "The Equator";
+
+        // Draw a line in the right colour
+        cairo_set_source_rgb(s->cairo_draw, s->equator_col.red, s->equator_col.grn, s->equator_col.blu);
+        cairo_new_path(s->cairo_draw);
+        cairo_move_to(s->cairo_draw, x * s->cm, y1 * s->cm);
+        cairo_line_to(s->cairo_draw, (x + size) * s->cm, y1 * s->cm);
+        cairo_stroke(s->cairo_draw);
+
+        // Write a text label next to it
+        cairo_set_source_rgb(s->cairo_draw, 0, 0, 0);
+        cairo_text_extents(s->cairo_draw, label, &extents);
+        cairo_move_to(s->cairo_draw,
+                      (x + 0.1 + size * 1.25) * s->cm - extents.x_bearing,
+                      y1 * s->cm - extents.height / 2 - extents.y_bearing
+        );
+        cairo_show_text(s->cairo_draw, label);
+
+        // Advance horizontally to draw the next item in the legend
+        x += w_item;
+    }
+
         // Draw a line in the right colour
         cairo_set_source_rgb(s->cairo_draw, s->ecliptic_col.red, s->ecliptic_col.grn, s->ecliptic_col.blu);
         cairo_new_path(s->cairo_draw);

src/astroGraphics/greatCircles.h

@@ -31,6 +31,8 @@
 
 void plot_equator(chart_config *s, line_drawer *ld, cairo_page *page);
 
+void plot_meridian(chart_config *s, line_drawer *ld, cairo_page *page);
+
 void plot_galactic_plane(chart_config *s, line_drawer *ld, cairo_page *page);
 
 void plot_ecliptic(chart_config *s, line_drawer *ld, cairo_page *page);

src/astroGraphics/raDecLines.c

@@ -144,7 +144,8 @@ void plot_ra_dec_lines(chart_config *s, line_drawer *ld) {
 
         // Tell the line drawing class what label should be placed on the edge of the star chart when we cross it
         // Lines of constant RA only create tick labels on the horizontal axes, not the vertical axes
-        ld_label(ld, label, 1, 0);
+	// Lines of constant declination create a tick on the round edge of the chart in Alt_Az mode if and only if ordered to do so
+        ld_label(ld, label, 1, 0, s->ra_ticks_on_round_edge);
 
         // Trace the path of this line across chart
         for (j = 0; j < N_POINTS; j++) {
@@ -214,7 +215,8 @@ void plot_ra_dec_lines(chart_config *s, line_drawer *ld) {
 
         // Tell the line drawing class what label should be placed on the edge of the star chart when we cross it
         // Lines of constant declination only create tick labels on the vertical axes, not the horizontal axes
-        ld_label(ld, label, 0, 1);
+	// Lines of constant declination create a tick on the round edge of the chart in Alt_Az mode if and only if ordered to do so
+        ld_label(ld, label, 0, 1, s->dec_ticks_on_round_edge);
 
         // Trace the path of this line across chart
         for (j = 0; j < N_POINTS; j++) {

src/main.c

@@ -80,11 +80,14 @@ void render_chart(chart_config *s) {
     plot_background_image(s);
 
     // Initialise module for tracing lines on the star chart
-    ld_init(&ld, s, page.x_labels, page.x2_labels, page.y_labels, page.y2_labels);
+    ld_init(&ld, s, page.x_labels, page.x2_labels, page.y_labels, page.y2_labels, page.r_labels);
 
     // Draw the line of the equator
     if (s->plot_equator) plot_equator(s, &ld, &page);
 
+    // Draw the line of the vernal meridian
+    if (s->plot_meridian) plot_meridian(s, &ld, &page);
+
     // Draw the line of the galactic plane
     if (s->plot_galactic_plane) plot_galactic_plane(s, &ld, &page);
 
@@ -350,7 +353,19 @@ int main(int argc, char **argv) {
             CHECK_KEYVALNUM("axis_ticks_value_only")
             settings_destination->axis_ticks_value_only = (int) key_val_num;
             continue;
-        } else if (strcmp(key, "axis_label") == 0) {
+        } else if (strcmp(key, "ra_ticks_on_round_edge") == 0) {
+            //! ra_ticks_on_round_edge - If 1, constant RA labels will place ticks on the round edge in Alt_Az mode. 
+	    //! If 0, they won't
+            CHECK_KEYVALNUM("ra_ticks_on_round_edge")
+            settings_destination->ra_ticks_on_round_edge = (int) key_val_num;
+            continue;
+	} else if (strcmp(key, "dec_ticks_on_round_edge") == 0) {
+//! dec_ticks_on_round_edge - If 1, constant Dec labels will place ticks on the round edge in Alt_Az mode.                   
+            //! If 0, they won't		
+	    CHECK_KEYVALNUM("dec_ticks_on_round_edge")
+            settings_destination->dec_ticks_on_round_edge = (int) key_val_num;
+            continue;
+	} else if (strcmp(key, "axis_label") == 0) {
             //! axis_label - Boolean (0 or 1) indicating whether to write "Right ascension" and "Declination" on the
             //! vertical/horizontal axes
             CHECK_KEYVALNUM("axis_label")
@@ -476,7 +491,7 @@ int main(int argc, char **argv) {
             } else if (strcmp(key_val, "alt_az") == 0) {
                 settings_destination->projection = SW_PROJECTION_ALTAZ;
                 settings_destination->aspect = 1.;
-                settings_destination->angular_width = 180.;
+		//settings_destination->angular_width = 180.;
             } else {
                 snprintf(temp_err_string, FNAME_LENGTH,
                          "Bad input file. projection should equal 'flat', 'gnomonic', 'sphere' or 'alt_az'.");
@@ -720,7 +735,18 @@ int main(int argc, char **argv) {
             CHECK_KEYVALNUM("plot_equator")
             settings_destination->plot_equator = (int) key_val_num;
             continue;
-        } else if (strcmp(key, "ecliptic_col") == 0) {
+	}else if (strcmp(key, "plot_meridian") == 0) {
+            //! plot_meridian - Boolean (0 or 1) indicating whether to draw a line along the vernal meridian
+            CHECK_KEYVALNUM("plot_meridian")
+            settings_destination->plot_meridian = (int) key_val_num;
+            continue;
+	} else if (strcmp(key, "label_meridian") == 0) {
+            //! label_meridian - Boolean (0 or 1) indicating whether to label Dec degrees along the
+            //! vernal meridian, useful to label Dec lines in Alt_Az charts
+            CHECK_KEYVALNUM("label_meridian")
+            settings_destination->label_meridian = (int) key_val_num;
+            continue;
+	} else if (strcmp(key, "ecliptic_col") == 0) {
             //! ecliptic_col - Colour to use when drawing a line along the ecliptic
             settings_destination->ecliptic_col = colour_from_string(key_val);
             continue;
@@ -732,6 +758,10 @@ int main(int argc, char **argv) {
             //! equator_col - Colour to use when drawing a line along the equator
             settings_destination->equator_col = colour_from_string(key_val);
             continue;
+	} else if (strcmp(key, "meridian_col") == 0) {
+            //! meridian_col - Colour to use when drawing a line along the equator
+            settings_destination->meridian_col = colour_from_string(key_val);
+            continue;
         } else if (strcmp(key, "plot_galaxy_map") == 0) {
             //! plot_galaxy_map - Boolean (0 or 1) indicating whether to draw a shaded map of the Milky Way behind
             //! the star chart