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Created Datum transformation tutorial
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‎README.md‎

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This is a package of tools for manipulating geospatial datasets using Python and tested in Python 3.6.4.
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### Tutorials
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### Documentation
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See [here](https://github.com/GeoscienceAustralia/GeodePy/tree/master/docs/tutorials) for worked examples of common GeodePy functions and routines.
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See [here](https://geodepy.readthedocs.io/) for documentation around downloading and using GeodePy.
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### Dependencies
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‎docs/features/constants.rst‎

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.. autoclass:: geodepy.constants.Projection
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:members:
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.. _transclass:
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.. autoclass:: geodepy.constants.Transformation
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:members:
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| isg | Projection | Integrated Survey Grid (NSW, AGD66) |
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+-----------------------------+---------------------+-------------------------------------------------------------+
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.. _features/constants/transform:
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Transformation
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^^^^^^^^^^^^^^
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‎docs/tutorials/edmcorrectiontut.rst‎

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Using these we can calculate the first velocity correction and reduce to a horizontal distance.
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First the variables need to be defined. Below is the values for a Lecia Viva
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First the variables need to be defined. Below is the values for a Lecia Viva.
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.. code:: python
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‎docs/tutorials/timedeptranstut.rst‎

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.. _tutorials/timetrans:
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Time Dependant Transformations
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==============================
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==============================
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In this tutorial we will discuss time dependant transformations where the reference epoch needs to be changed.
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To see transformations between static datums view the :ref:`datum transformation <tutorials/transform>` tutorial.

‎docs/tutorials/transformtut.rst‎

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.. _tutorials/transform:
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Datum Transformation
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=====================
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=====================
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GeodePy has the ability to tranform between datums. Here we will discuss how to
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change between datums without changing the reference epoch while in the
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:ref:`time dependant <tutorials/timetrans>` tutorial we will discuss changing epochs.
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Common Example
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--------------
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The most common example for datum transformation is converting from MGA94 to MGA2020.
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This is handled by a function in the transformation module that converts the input to
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grid input to caresian coordinate (xyz), and then runs a 7 paramter helmert transformation
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using the GDA94_to_gda2020 transformation constant. This process will be explored more in
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the :ref:`latter <tutorials/transformfunc>` part of this tutorial but first lets use this function.
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Begin by importing GeodePy:
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.. code:: python
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import geodepy.transform
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Next, define some coordinate values in MGA94:
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.. code:: python
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zone_94 = 55
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east_94 = 696053.3373
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north_94 = 6086610.1338
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Now, transform this coordinate to MGA2020:
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.. code:: python
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(zone_20, east_20, north_20, _, _) = geodepy.transform.transform_mga94_to_mga2020(
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zone_94,
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east_94,
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north_94
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)
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Finally, print the transformed coordinate:
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.. code:: python
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print(zone_20, east_20, north_20)
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This will output the zone, easting and northing of the coordinate in MGA2020.
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.. code::
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>> 55 696053.872 6086611.549
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In this transformation you can see that a function from the transformation module was used.
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.. _tutorials/transformfunc:
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Constructing a new Transformation Function
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------------------------------------------
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Here we will explore how to complete a transformation between datums without a dedicated function.
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We will then create a new function for this new transformation. Here we are going to transform between agd84 to gda2020
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First import GeodePy.
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.. code:: python
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import geodepy.transform
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import geodepy.constants
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import geodepy.angles
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Now we need some starting coordinates
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.. code:: python
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lat = geodepy.angles.DMSAngle(-23,33,25.21)
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long = geodepy.angles.DMSAngle(133,49,13.87)
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height = 427.863
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print(f"The AGD84 position is {lat}, {long}, {height}"
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>>The AGD84 position is -23 33 25.21, 133 49 13.87, 427.863
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All transformations in GeodePy need to be completed with corrdinates in cartesian (xyz) form. Lets transform to xyz.
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.. code:: python
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x, y, z = geodepy.transform.llh2xyz(lat, long, height)
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print(x, y, z)
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>>-4050634.051819 4220935.13646 -2533555.369303
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Now the transformation parameters need to be entered. Within Geodepy there are many transformaton parameters already
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entered within the constants module. A table of these can be seen :ref:`here <features/constants/transform>`. If the
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transformation needed isn't currently in Geodepy, new transofmrations can be added using the :ref:`transformation class <transclass>`.
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Here the agd66_to_gda94 transformation will be used.
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.. code:: python
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print(geodepy.constants.agd84_to_gda94)
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>>Transformation: From 'AGD84' to 'GDA94'
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>>Reference Epoch: 0
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>>tx: -117.763m + 0.0m/yr
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>>ty: -51.51m + 0.0m/yr
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>>tz: 139.061m + 0.0m/yr
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>>sc: -0.191ppm + 0.0ppm/yr
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>>rx: -0.292" + 0.0"/yr
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>>ry: -0.443" + 0.0"/yr
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>>rz: -0.277" + 0.0"/yr
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Now this will be used to complete a 7 paramter helmert transformation.
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.. code:: python
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x_94, y_94, z_94, _ = geodepy.transform.conform7(x, y, z, geodepy.constants.agd84_to_gda94)
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print(x_94, y_94, z_94)
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>>-4050762.150962 4220880.96717 -2533401.14935
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.. tip::
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The "_" in the conform7 variables is for a vcv matrix. If you dont input a vcv matrix
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then the resulting variable will be None. However as the variable needs to be assigned
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for the function to work using "_" meets to requirement but doesn't store the variable
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in a meaningful way.
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Now we need to transform from GDA94 to GDA2020 using the same method but with the gda94_to_gda2020
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transformation class.
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.. code:: python
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x_20, y_20, z_20, _ = geodepy.transform.conform7(x_94, y_94, z_94, geodepy.constants.gda94_to_gda2020)
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print(x_20, y_20, z_20)
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>>-4050763.124034 4220880.75310 -2533399.713463
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Now the cartesian coordinates can be converted back to geographic coordinates (lat, long)
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.. code:: python
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lat_20, long_20, height_20 = geodepy.transform.xyz2llh(x_20, y_20, z_20)
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print(f"The GDA2020 position is {geodepy.angles.dec2dms(lat_20)}, {geodepy.angles.dec2dms(long_20)}, {height_20}")
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>>The GDA2020 position is -23 33 19.921108332, 133 49 18.481110119, 411.61055134
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All of this can now be combined into one function.
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.. code:: python
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def transform_agd84_to_gda2020(lat, long, height):
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x, y, z = geodepy.transform.llh2xyz(lat, long, height)
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x_94, y_94, z_94, _ = geodepy.transform.conform7(x, y, z, geodepy.constants.agd84_to_gda94)
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x_20, y_20, z_20, _ = geodepy.transform.conform7(x_94, y_94, z_94, geodepy.constants.gda94_to_gda2020)
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return geodepy.transform.xyz2llh(x_20, y_20, z_20)
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lat_new, long_new, height_new = transform_agd84_to_gda2020(lat, long, height)
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print(f"The GDA2020 position is {geodepy.angles.dec2dms(lat_new)}, {geodepy.angles.dec2dms(long_new)}, {height_new}")
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>>The GDA2020 position is -23 33 19.921108332, 133 49 18.481110119, 411.61055134
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