A system, comprising: an implantable stimulator device (10; 110; 50; 150), comprising: a plurality of electrode nodes, each electrode node configured to be coupled to one of a plurality of electrodes configured to contact a patient's tissue, and first control circuitry configured to execute an algorithm configured to provide at least one test current between at least two of the electrodes nodes, and in response to the at least one test current measure a voltage data set at at least some of the plurality of electrode nodes; and an external device (60; 70) configured to communicate with the implantable stimulator device (10; 110; 50; 150), the external device (60; 70) comprising: second control circuitry (66; 88) configured to render a graphical user interface, wherein the graphical user interface comprises a first input to cause the first control circuitry in the implantable stimulator device (10; 110; 50; 150) to execute the algorithm, receive the voltage data set from the implantable stimulator device (10; 110; 50; 150), and determine a representation of an electric field in the patient's tissue using the received voltage data set and using potential stimulation parameters for the patient. an implantable stimulator device (10; 110; 50; 150), comprising: a plurality of electrode nodes, each electrode node configured to be coupled to one of a plurality of electrodes configured to contact a patient's tissue, and first control circuitry configured to execute an algorithm configured to provide at least one test current between at least two of the electrodes nodes, and in response to the at least one test current measure a voltage data set at at least some of the plurality of electrode nodes; and a plurality of electrode nodes, each electrode node configured to be coupled to one of a plurality of electrodes configured to contact a patient's tissue, and first control circuitry configured to execute an algorithm configured to provide at least one test current between at least two of the electrodes nodes, and in response to the at least one test current measure a voltage data set at at least some of the plurality of electrode nodes; and an external device (60; 70) configured to communicate with the implantable stimulator device (10; 110; 50; 150), the external device (60; 70) comprising: second control circuitry (66; 88) configured to render a graphical user interface, wherein the graphical user interface comprises a first input to cause the first control circuitry in the implantable stimulator device (10; 110; 50; 150) to execute the algorithm, receive the voltage data set from the implantable stimulator device (10; 110; 50; 150), and determine a representation of an electric field in the patient's tissue using the received voltage data set and using potential stimulation parameters for the patient. render a graphical user interface, wherein the graphical user interface comprises a first input to cause the first control circuitry in the implantable stimulator device (10; 110; 50; 150) to execute the algorithm, receive the voltage data set from the implantable stimulator device (10; 110; 50; 150), and determine a representation of an electric field in the patient's tissue using the received voltage data set and using potential stimulation parameters for the patient.