Doc: Fixed mistake in info about isophotal measurements.

Doc: Fixed broken ref to Background Modeling section.

doc/src/Background.rst

@@ -2,6 +2,8 @@
 
 .. include:: global.rst
 
+.. _background_model:
+
 Modeling the background
 =======================
 

doc/src/Measurements.rst

@@ -11,7 +11,7 @@ Once sources have been detected and deblended, they enter the measurement phase.
 .. _isophotal_measurements:
 
 Isophotal
-  Measurements are made on the isophotal object footprints, which are defined on the filtered detection image. Only pixels with values above the threshold set with ``ANALYSIS_THRESH`` are considered [#thresh]_, which makes the analysis extremely fast, but obviously strongly dependent on the threshold itself. This is an issue particularly when the amplitude of the bakground noise varies over the image. Many of the isophotal measurements (e.g., :param:`X_IMAGE`, :param:`Y_IMAGE`, :param:`FLUX_ISO`) are necessary for the internal operations of |SExtractor| and are therefore executed even if they are not requested.
+  Measurements are made on the isophotal object footprints, which are defined on the filtered detection image. Only pixels with values above the detection threshold (set with ``DETECT_THRESH``) are considered [#thresh]_, which makes the analysis extremely fast, but obviously strongly dependent on the threshold itself. This is an issue particularly when the amplitude of the bakground noise varies over the image. Many of the isophotal measurements (e.g., :param:`X_IMAGE`, :param:`Y_IMAGE`, :param:`FLUX_ISO`) are necessary for the internal operations of |SExtractor| and are therefore executed even if they are not requested.
 
 Full
   Measurements have access to all pixels of the image. These measurements are generally more sophisticated, less affected by variable biases induced by the detection threshold, and still reasonably fast. They are done at a later stage of the processing, after CLEANing and MASKing.
@@ -27,7 +27,7 @@ Model-fitting
   Model
   ClassStar
 
-.. [#thresh] Pixel values also have to exceed the local detection threshold set with ``DETECT_THRESH``.
+.. [#thresh] For some isophotal measurements pixel values also have to exceed the local analysis threshold set with ``ANALYSIS_THRESH``.
 .. [#psf_models] PSF models be computed using the |PSFEx|_ package.
 
 

doc/src/Photom.rst

@@ -249,7 +249,7 @@ Local background
 ----------------
 
 Almost all |SExtractor| measurements are done using background-subtracted pixel values.
-In crowded fields, or in images where the background is irregular, the :ref:`background model` may be significantly inaccurate, locally creating biases in photometric estimates.
+In crowded fields, or in images where the background is irregular, the :ref:`background model <background_model>` may be significantly inaccurate, locally creating biases in photometric estimates.
 
 The user has the possibility to force |SExtractor| to correct, for every detection, the background used to compute fluxes by setting the ``BACKPHOTO_TYPE`` configuration parameter to ``LOCAL`` (``GLOBAL`` is the default).
 In ``LOCAL`` mode, a mean background residual level is estimated from background-subtracted pixel values within a "rectangular annulus" around the isophotal limits of the object.