Example: Edit Attributes and Move a Point

We look at the attributes for a point in a drawing layer and edit one of the attributes using a more expanded Edit dialog.  We then move the point to a new location. Easy!    This example has been published as the Manifold Future - Future Tour Part 4 Edit Attributes, Move a Point  video on the Manifold Sales YouTube channel.  


We will make an addition and a correction to the database of Neolithic sites used in the Select and Transform a Neolithic Relics Database video.  Specifically, we will expand the text commentary that is in one of the attribute fields for a dolmen, a type of stone construction from Neolithic times that is found in many parts of France.



The image above shows a typical Neolithic dolmen, with a table rock (the flat upper rock) being not quite two meters (six feet) across.   A dolmen usually has a flat table rock placed upon three or more upright flat stones to create a small stone room or chamber.  Dolmens apparently were originally covered with a mound of earth, like an artificial hill, so that what we see today would have been the stone construction that created a chamber within the hill. Today, almost all dolmens have had their covering hills eroded away.  Most were erected from 4000 to 6000 years ago.  Hundreds can be found in France.



The map above shows hundreds of points, styled by color and size to indicate different sites and different types of Neolithic monuments in France.    We have clicked on the Megalithe_FR Drawing layer, which contains the displayed objects, to make it the active layer.


We select the dolmen called DLSOU0 2, and then right-click onto the drawing's tab and choose Zoom to Selection.  



Adjusting zoom a bit, and choosing Edit - Select None to deselect the point, we see what the database contains the wrong location, marked by a cyan dot, for a dolmen.   To the right is a wooded area and lower to the left is the true location of the dolmen, visible on the Google satellite image and marked with a magenta arrow.



Zoomed further in to the point, the Google satellite layer shows nothing but an empty farmer's field at the dot.   



In the field nearby we see what at high zoom level, a scale of 1:300, looks like a larger-than-average dolmen, surrounded by a cleared area.  



Using the tracker tool we measure the dolmen, and see the object in view is 3.3 meters long, the size of the table rock cited in the DLSOU0 2 entry in the table.   From the air, it appears as typical, fallen dolmen, hundreds of which are found in this part of France.


In the past, especially after the invention of dynamite, farmers annoyed with multi-ton stone constructions blocking their plowing would often blow up and remove dolmens from their fields.  In modern times, dolmens in France are often protected in wooded areas, small parks, or clearings within farmed fields.    




This particular dolmen can be reached by dirt road from a nearby paved road.  It is barely visible on Google Street View from the D130 road running nearby if we zoom Street View to maximum magnification in the direction of the dolmen.

Editing Attributes


We will begin by seeing the attributes, that is, the field values for this object.  To do that, at the bottom of the map we click the layer containing the dot to make sure it is the active layer and then we Alt-click the dot.



That immediately marks the dot with blue preview color as our picked object, surrounded by a box to make it easier to find the picked point.   Alt-clicking the point also opens the Info pane.



The Info pane automatically opens to the Values tab to show field values (also known as attributes in GIS jargon) for the Alt-clicked point.   Since this is a French database the information is in French.   To see the full text of the Description field we can right-click on it.



We choose Edit from the resulting context menu.



That launches a larger editing dialog that shows the full text in that field.   We can se that the table rock is 3.3 meters in size, over ten feet, which makes this dolmen a larger than average dolmen, but that the dolmen has collapsed with the table rock lying next to the fallen vertical rocks.   The dialog allows us to make edits to the text, such as adding additional text.



We add additional text to further describe the dolmen found in that location.    We press OK.


A 1km au Nord d'Eteauville, dans un champ. Sa table de 3,30 m repose à côté de trois piliers tombés.


La légende locale raconte que Gargantua, se rendant dans la Beauce dunoise par l'ancienne voie d'Allaines à Châteaudun, s'arrêta en cet endroit et, voyant ces pierres, s'amusa à jongler avec elles en manière de passe-temps.


The full text for the record, for those who do not read French but who would like to give an online translator a try, is given above.   C'est bon!



The edited field is indicated in blue preview color.   We can abandon the edit with a Ctrl-Backspace, if desired.   To accept the edit, we press the Update Record button.

Editing Geometry - Moving a Point

The point is still marked in the map window with a blue dot to indicate it is the picked object for which attributes are displayed in the Values tab.   However, it cannot be moved in the map window until we switch into an editing mode, like Move Coordinates.   



We can switch into Move Coordinates mode and enable the point for editing by clicking on the Coordinates tab.



That displays the values of the coordinates for the location of the point.   If the picked object had been a line or area we would see a list of coordinates for the list of vertices that defined the shape of the line or the area.


We can switch into Move Coordinates mode using mouse moves within the map window by clicking the point again in the map.  We can also right-click into the map and choose Move Coordinates mode from the context menu.

Attributes are not Geometry

Keep in mind that points in Manifold are objects that are defined by geometry fields, typically named Geom, that contain the geometric definition of objects like points, lines, and areas, using a data type of geom.  A geom value contains an internal list of coordinates that specifies the location of a point, that specifies the sequence of coordinates that defines a line, and that specifies the sequence of coordinates that defines an area by defining the closed boundary of the area.


Tables that contain records for points often contain latitude and longitude attribute fields in addition to the Geom field that contains the actual points.    We can see that in action in this example by comparing the Values tab and the Coordinates tab for this particular point record:



We can see from the record for one point that the table has a field called Geom that contains a geom data type that stores the geometry for the point.  It also has attribute fields like the Name field and a Description field, and it also has a Latitude and a Longitude field.  In this case the Latitude and a Longitude fields were imported from the original French data set, but now they no longer define the geometry.  They simply are along for the ride, since the drawing's geometry, that is, the actual location of the point object in each record, is defined by the geometry data in the Geom field.


Tables often contain latitude and longitude fields in addition to the geom geometry field for two main reasons:  


First, the geom field is often created from a geocoded table that started out as a list of latitudes and longitudes that gave the location for desired points, which were then used to create the drawing, including the geometry field that powers the drawing, using a process like that described in the Example: Create a Drawing from a Geocoded Table topic.   Once the geom is created, the geom field is used to display the points in a map.  The coordinates encoded inside the geom define the points, and once it is created any latitude and longitude fields that were used to create the geom can be discarded.   In the example above, if we deleted the Latitude and the Longitude fields from the table the Geom field would still be there and the points will still be there.  


Second, although geom fields are a super fast and powerful way of telling a GIS where a point is located, they are not human readable when scanning a table by eye, and other applications may not be able to understand binary representations of locations like the encoded coordinates within a geom.  Therefore, tables that have geom fields to enable drawings to show the points in them will often also have latitude and longitude fields that report the location for the point as human readable numbers.  Such numbers can also be provided to other programs which can use them to plot points in whatever internal systems those other programs use.


That can be confusing in cases, like this topic, where the initial values that were used to create the point geometry were wrong.  If we reach directly into the point's geometry geom field and change the coordinates there by moving the point, that will change the coordinates that are encoded inside the geom but it will not change the attributes that were used some time in the past to create the geom.  


If we would like to have human readable latitude and longitude fields in our table that are automatically synchronized to whatever coordinates are inside the geom, we can do that by creating latitude and longitude fields that are computed fields:  those will be automatically computed on the fly from the geom.  In that case, if we change the coordinates inside the geom by dragging the point to a new location, or by editing the values in the Coordinates tab, the human readable latitude and longitude fields will automatically be recomputed to whatever are the new coordinate values inside the geom.


The procedure for creating such computed fields is illustrated step-by-step in the Example: Create a Geocoded Table from a Drawing  topic.

The Example Continues


When we click on the Coordinates tab, in addition to displaying coordinates for the point that also enables Move Coordinates mode in the map window, enabling the point for editing.  The small blue marker expands to a larger blue square to indicate the point is in play for editing.   


Having to choose the Coordinates tab, or having to click the point again, is a safety measure so we can Alt-click on an object to see its attributes without immediately enabling the object for editing as well.



To move the point to a new location we can simply drag it to whatever location desired.  In the above illustration we drag the point from the wrong location to the true location of the dolmen in the field.


When we do that the coordinate values in the Coordinates tab change to the new location and are displayed in blue preview color.   To abandon the edit we could press Ctrl-Backspace and the point would pop back into its original position.  To accept the edit we press the Update Record button.    To accept or abandon the edit we could also right-click into the map and choose Save Changes or Undo Changes in the context menu.



When we press the Update Record button the edit is committed and the Info pane snaps back to the Values tab.  


 The Latitude and Longitude attributes for the record have not changed, because those have no connection to the geometry field.  Those are the original values in a table for the supposed latitude and longitude of the dolmen, which might have been used to create the geom value for the point that actually places the point, but which now are just along for the ride.  When we edited the coordinates inside the geom (which is what moving the point or editing inside the Coordinates tab does), we edited the geometry but we did not edit other fields, making no changes to the Name, to the Rank, or to the Latitude and Longitude fields.  The other attribute fields have no connection to what is in the Geom field.



In the map window, since we are now back in the Values tab the object is no longer in Move Coordinates mode, enabled for geometry editing.  It now is marked with a small blue marker.   To eliminate that, that is, to not pick any object for display in the Record pane, we can Alt-click anywhere in the drawing away from the object.   In the view above we have zoomed further into the display so we can more clearly see how we dragged the point exactly onto the dolmen.



We can see the cyan dot marking the location of that particular dolmen has been moved from the wrong location, from a field where no dolmen is located, to the correct location.



We have placed the dot just slightly to one side of the top of the dolmen in the field  Now would be a good time to save the project.


See Also

Getting Started


User Interface Basics






Editing Drawings


Layers Pane


Info Pane


Example: Edit Coordinates While Creating an Object - When creating an object in a map using a tool such as Create Area, right in the middle of the process we can edit coordinates in the Info pane Coordinates tab.   This example shows the step by step process.


Example: Edit Attributes, Larger Text, IME for Asian Languages - A tour showing how to edit attributes in a drawing using the Info pane Values tab and the expanded Edit dialog, including advanced Unicode facilities and use of the built in Input Method Editor (IME) to input text in Japanese language.


Example: Edit Covered Objects - Working with drawings where some areas completely cover smaller areas is a bad idea, but sometimes we have to work with data in that form whether we like it or not.   This topic shows techniques that can help us select and edit objects that are completely hidden by higher objects.


Editing Drawings - Create Areas - How to create areas (polygons) in a drawing.  We digitize a lake by tracing over a background satellite image layer from a web server.  This quick video shows how editing tools in Manifold make it easy to digitize objects very quickly, correcting any errors with no stress or fear of getting it wrong.  Includes a quick demo of snapping.


Editing Drawings - Create Lines with Curves - A very short video showing how to create lines in drawings using straight segments and also circular arcs.  We create a line in a map of Paris showing our walk around circular ponds. Manifold can create polylines using straight line segments for classic polylines, or using curved segments that are circular arcs, ellipses, or splines for very smooth curves, a much faster and easier technique than clicking many points.  Super!


Manifold Future - Future Tour Part 5 Unicode Attributes and IME -  We take a tour through Manifold Future attribute editing, showing how to edit attributes in a drawing using the Info pane Values

tab and the expanded Edit dialog, including advanced Unicode facilities and use of the built in Input Method Editor (IME) to input text in Japanese language.


Manifold Future - Future Tour Part 6 Cell Context Menu - A short video showing a fast and easy way to copy between cells in tables using the context menu.  Also... one step undo of pending changes,  setting the value of a cell to NULL and more. The context menu on cells is such a simple thing but it makes repetitive editing of tables much faster and easier.